Apparatus and method for performing power calibration in wireless power transmission system

ABSTRACT

The present invention relates to an apparatus and a method for performing power calibration in a wireless power transmission system. The present specification provides a wireless power transmission apparatus comprising: a power conversion unit configured to transmit, in a power transfer phase, wireless power generated on the basis of magnetic coupling to a wireless power receiving device; and a communication/control unit configured to perform an initial calibration for a power parameter prior to the power transfer phase, receive a first received power packet from the wireless power receiving device indicating the power received by the wireless power receiving device during the power transfer phase, and detect foreign matter by using the received power and a first power loss determined on the basis of the initial calibration. It is possible to adaptively respond to a newly changed wireless charging environment to calibrate transmission power and reception power, and it is possible to detect foreign matter more precisely by detecting a power loss on the basis of the calibrated transmission and reception power.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.17/449,884, filed on Oct. 4, 2021, which is a continuation of U.S.patent application Ser. No. 16/961,554, filed on Jul. 10, 2020,patented, now U.S. Pat. No. 11,139,702, which is the National Stagefiling under 35 U.S.C. 371 of International Application No.PCT/KR2019/000251, filed on Jan. 8, 2019, which claims the benefit ofU.S. Provisional Application No. 62/615,445, filed on Jan. 10, 2018, thecontents of which are all hereby incorporated by reference herein intheir entireties.

TECHNICAL FIELD

The present disclosure relates to wireless charging, and moreparticularly, to an apparatus and method for performing powercalibration in a wireless power transfer system.

BACKGROUND ART

The wireless power transfer (or transmission) technology corresponds toa technology that can wirelessly transfer (or transmit) power between apower source and an electronic device. For example, by allowing thebattery of a wireless device, such as a smartphone or a tablet PC, andso on, to be recharged by simply loading the wireless device on awireless charging pad, the wireless power transfer technique may providemore outstanding mobility, convenience, and safety as compared to theconventional wired charging environment, which uses a wired chargingconnector. Apart from the wireless charging of wireless devices, thewireless power transfer technique is raising attention as a replacementfor the conventional wired power transfer environment in diverse fields,such as electric vehicles, Bluetooth earphones, 3D glasses, diversewearable devices, household (or home) electric appliances, furniture,underground facilities, buildings, medical equipment, robots, leisure,and so on.

The wireless power transfer (or transmission) method is also referred toas a contactless power transfer method, or a no point of contact powertransfer method, or a wireless charging method. A wireless powertransmission system may be configured of a wireless power transmittersupplying electric energy by using a wireless power transfer method, anda wireless power receiver receiving the electric energy being suppliedby the wireless power transmitter and supplying the receiving electricenergy to a receiver, such as a battery cell, and so on.

The wireless power transfer technique includes diverse methods, such asa method of transferring power by using magnetic coupling, a method oftransferring power by using radio frequency (RF), a method oftransferring power by using microwaves, and a method of transferringpower by using ultrasound (or ultrasonic waves). The method that isbased on magnetic coupling is categorized as a magnetic induction methodand a magnetic resonance method. The magnetic induction methodcorresponds to a method transmitting power by using electric currentsthat are induced to the coil of the receiver by a magnetic field, whichis generated from a coil battery cell of the transmitter, in accordancewith an electromagnetic coupling between a transmitting coil and areceiving coil. The magnetic resonance method is similar to the magneticinduction method in that is uses a magnetic field. However, the magneticresonance method is different from the magnetic induction method in thatenergy is transmitted due to a concentration of magnetic fields on botha transmitting end and a receiving end, which is caused by the generatedresonance.

A wireless power transmitter and a wireless power receiver includevarious circuit components provided therein and are constituted asindependent devices from each other, but since the wireless powertransfer is performed by magnetically coupling between the wirelesspower transmitter and the wireless power receiver, the wireless powertransmitter and the wireless power receiver constitute one wirelesspower transfer system. However, an error may occur between thetransmitted power and received power due to a change in the magneticcoupling according to the actual use environment (signal size,frequency, and duty cycle applied to the wireless power transfer system,distance/position alignment between Tx and the Rx, and the like) of Txand Rx as well as unique physical characteristics of the wireless powertransfer system. The error may be an obstacle to a sophisticateddetection of foreign object.

Therefore, there is a need for a method of calibrating transmitted powerand received power by reflecting the unique characteristics of thewireless power transfer system and the change in the actual useenvironment, and performing more sophisticated FOD based on thecalibrated transmitted power and received power.

DISCLOSURE Technical Problem

The technical problem of the present disclosure is to provide anapparatus and method for performing power calibration in a wirelesspower transfer system.

Another technical problem of the present disclosure is to provide anapparatus and method for adaptively performing power calibration inresponse to a change in load and performing a detection of foreignobject.

Still another technical problem of the present disclosure is to providean apparatus and method for adaptively performing power calibration inresponse to a change in magnetic coupling between a wireless powertransmitter and a wireless power receiver, and performing a detection offoreign objects.

Technical Solution

According to an aspect of the present disclosure, there is provided awireless power transmitter including a power conversion unit configuredto transmit wireless power generated based on magnetic coupling to awireless power receiver in a power transfer phase, and acommunication/control unit configured to perform initial calibration fora power parameter before the power transfer phase, receive, from thewireless power receiver, a first received power packet informing thepower received by the wireless power receiver during the power transferphase, and perform a detection of foreign objects using the receivedpower and a first power loss determined based on the initialcalibration.

Here, the communication/control unit may be configured to performsubsequent calibration for the power parameter and perform the detectionof the foreign objects using a second power loss determined based on thesubsequent calibration.

In one aspect, the communication/control unit may receive a secondreceived power packet from the wireless power receiver during the powertransfer phase, the first received power packet may include a first modefield informing that a first received power value informed by the firstreceived power packet is a normal value, and the second received powerpacket may include a second mode field informing that a received powervalue informed by the second received power packet is a second receivedpower value in a connected load state.

In another aspect, the power parameter before the power transfer phasemay include a light load received power value received by the wirelesspower receiver under a condition that no load is connected to thewireless power receiver and a connected load received power valuereceived by the wireless power receiver under a condition that the loadis connected to the wireless power receiver, the power parameter duringthe power transfer phase may include the second received power value,and the communication/control unit may perform the subsequentcalibration based on the light load received power value, the connectedload received power value, and the second received power value.

In another aspect, the communication/control unit may transmit a bitpattern requesting an initiation of re-ping to the wireless powerreceiver based on the change in the magnetic coupling.

In another aspect, the communication/control unit may receive a re-pinginitiation packet from the wireless power receiver in response to thebit pattern.

In another aspect, the re-ping initiation packet may include an endpower transfer (EPT) packet for initiating the re-ping.

In another aspect, the communication/control unit may enter a re-pingphase based on the re-ping initiation packet, and perform the initialcalibration again in the re-ping phase.

According to another aspect of the present disclosure, there is provideda wireless power transmitter including a power pickup unit configured toreceive wireless power generated based on magnetic coupling to awireless power receiver in a power transfer phase, and acommunication/control unit configured to perform initial calibration fora power parameter before the power transfer phase and transmit, from thewireless power transmitter, a first received power packet informing thereceived power during the power transfer phase.

Here, the communication/control unit may be configured to perform thesubsequent calibration for the power parameter.

In one aspect, the communication/control unit may transmit a secondreceived power packet to the wireless power transmitter during the powertransfer phase, the first received power packet may include a first modefield informing that a first received power value informed by the firstreceived power packet is a normal value, and the second received powerpacket may include a second mode field informing that a received powervalue informed by the second received power packet is a second receivedpower value in a connected load state.

In another aspect, the power parameter before the power transfer phaseis a light load received power value received by the wireless powerreceiver under a condition that no load is connected to the wirelesspower receiver and a connected load received power value received by thewireless power receiver under a condition that the load is connected tothe wireless power receiver, and the power parameter during the powertransfer phase may include the second received power value.

In another aspect, when the magnetic coupling is changed to a certainlevel or higher, the communication/control unit may receive a bitpattern requesting an initiation of re-ping from the wireless powertransmitter.

In another aspect, the communication/control unit may transmit a re-pinginitiation packet from the wireless power receiver in response to thebit pattern.

In another aspect, the re-ping initiation packet may include an endpower transfer (EPT) packet for initiating the re-ping.

In another aspect, the communication/control unit may enter a re-pingphase based on the re-ping initiation packet, and perform the initialcalibration again in the re-ping phase.

According to another aspect of the present disclosure, there is provideda method for performing power calibration including: performing initialcalibration for a power parameter before a power transfer phase;transmitting wireless power generated based on magnetic coupling to awireless power receiver in the power transfer phase; receiving, from thewireless power receiver, a first received power packet informing powerreceived by the wireless power receiver during the power transfer phase;performing a detection of foreign objects using a first power lossdetermined based on the received power and the initial calibration;performing subsequent calibration on the power parameter; and performingthe detection of the foreign objects using the second power loss basedon the subsequent calibration.

In another aspect, the method may further include receiving a secondreceived power packet from the wireless power receiver during the powertransfer phase, in which the first received power packet may include afirst mode field informing that a first received power value informed bythe first received power packet is a normal value, and the secondreceived power packet may include a second mode field informing that areceived power value informed by the second received power packet is asecond received power value in a connected load state.

In another aspect, the power parameter before the power transfer phasemay include a light load received power value received by the wirelesspower receiver under a condition that no load is connected to thewireless power receiver and a connected load received power valuereceived by the wireless power receiver under a condition that the loadis connected to the wireless power receiver, the power parameter duringthe power transfer phase may include the second received power value,and the subsequent calibration may be performed based on the light loadreceived power value, the connected load received power value, and thesecond received power value.

In another aspect, the method may further include transmitting a bitpattern requesting an initiation of re-ping to the wireless powertransmitter based on the change in the magnetic coupling

Advantageous Effects

It is possible to more sophisticatedly detect the foreign objects bycalibrating the transmitted power and received power by adaptivelyreacting to the newly changed wireless charging environment anddetecting the power loss based on the calibrated transmitted power andreceived power.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a wireless power system (10) according toan embodiment.

FIG. 2 is a block diagram of a wireless power system (10) according toanother embodiment.

FIG. 3 shows an exemplary embodiment of diverse electronic devicesadopting a wireless power transmission system.

FIG. 4 is a block diagram of a wireless power transmission systemaccording to another embodiment.

FIG. 5 is a state transition diagram for describing a wireless powertransfer procedure.

FIG. 6 shows a power control method according to an embodiment.

FIG. 7 is a block diagram of a wireless power transmitter according toanother embodiment.

FIG. 8 shows a wireless power receiver according to another embodiment.

FIG. 9 shows a communication frame structure according to an embodiment.

FIG. 10 is a structure of a sync pattern according to an embodiment.

FIG. 11 shows operation statuses of a wireless power transmitter and awireless power receiver in a shared mode according to an embodiment.

FIG. 12 is a flowchart illustrating a method for performing powercalibration and a method for performing FOD according to an embodiment.

FIG. 13 is a diagram illustrating a received power packet according toan embodiment.

FIG. 14 is a diagram illustrating a calibration curve based on linearinterpolation according to an embodiment.

FIG. 15 is a flowchart illustrating a method for performing powercalibration according to a load increase event.

FIG. 16 is a flowchart illustrating a method for performing subsequentcalibration in a wireless power transmitter according to an embodiment.

FIG. 17 is a diagram illustrating an extended calibration curve based onlinear interpolation according to an embodiment.

FIG. 18 is a flowchart illustrating a method for performing powercalibration based on a coupling change event according to an embodiment.

FIG. 19 is a structural diagram illustrating an EPT packet forinitiating re-ping according to an embodiment.

FIG. 20 is a flowchart illustrating a method for performing powercalibration based on a coupling change event according to anotherembodiment.

MODE FOR DISCLOSURE

The term “wireless power”, which will hereinafter be used in thisspecification, will be used to refer to an arbitrary form of energy thatis related to an electric field, a magnetic field, and anelectromagnetic field, which is transferred (or transmitted) from awireless power transmitter to a wireless power receiver without usingany physical electromagnetic conductors. The wireless power may also bereferred to as a wireless power signal, and this may refer to anoscillating magnetic flux that is enclosed by a primary coil and asecondary coil. For example, power conversion for wirelessly chargingdevices including mobile phones, cordless phones, iPods, MP3 players,headsets, and so on, within the system will be described in thisspecification. Generally, the basic principle of the wireless powertransfer technique includes, for example, all of a method oftransferring power by using magnetic coupling, a method of transferringpower by using radio frequency (RF), a method of transferring power byusing microwaves, and a method of transferring power by using ultrasound(or ultrasonic waves).

FIG. 1 is a block diagram of a wireless power system (10) according toan embodiment.

Referring to FIG. 1 , the wireless power system (10) include a wirelesspower transmitter (100) and a wireless power receiver (200).

The wireless power transmitter (100) is supplied with power from anexternal power source (S) and generates a magnetic field. The wirelesspower receiver (200) generates electric currents by using the generatedmagnetic field, thereby being capable of wirelessly receiving power.

Additionally, in the wireless power system (10), the wireless powertransmitter (100) and the wireless power receiver (200) may transceive(transmit and/or receive) diverse information that is required for thewireless power transfer. Herein, communication between the wirelesspower transmitter (100) and the wireless power receiver (200) may beperformed (or established) in accordance with any one of an in-bandcommunication, which uses a magnetic field that is used for the wirelesspower transfer (or transmission), and an out-band communication, whichuses a separate communication carrier.

Herein, the wireless power transmitter (100) may be provided as a fixedtype or a mobile (or portable) type. Examples of the fixed transmittertype may include an embedded type, which is embedded in in-door ceilingsor wall surfaces or embedded in furniture, such as tables, an implantedtype, which is installed in out-door parking lots, bus stops, subwaystations, and so on, or being installed in means of transportation, suchas vehicles or trains. The mobile (or portable) type wireless powertransmitter (100) may be implemented as a part of another device, suchas a mobile device having a portable size or weight or a cover of alaptop computer, and so on.

Additionally, the wireless power receiver (200) should be interpreted asa comprehensive concept including diverse home appliances and devicesthat are operated by being wirelessly supplied with power instead ofdiverse electronic devices being equipped with a battery and a powercable. Typical examples of the wireless power receiver (200) may includeportable terminals, cellular phones, smartphones, personal digitalassistants (PDAs), portable media players (PDPs), Wibro terminals,tablet PCs, phablet, laptop computers, digital cameras, navigationterminals, television, electronic vehicles (EVs), and so on.

In the wireless power system (10), one wireless power receiver (200) ora plurality of wireless power receivers may exist. Although it is shownin FIG. 1 that the wireless power transmitter (100) and the wirelesspower receiver (200) send and receive power to and from one another in aone-to-one correspondence (or relationship), as shown in FIG. 2 , it isalso possible for one wireless power transmitter (100) to simultaneouslytransfer power to multiple wireless power receivers (200-1, 200-2, . . ., 200-M). Most particularly, in case the wireless power transfer (ortransmission) is performed by using a magnetic resonance method, onewireless power transmitter (100) may transfer power to multiple wirelesspower receivers (200-1, 200-2, . . . , 200-M) by using a synchronizedtransport (or transfer) method or a time-division transport (ortransfer) method.

Additionally, although it is shown in FIG. 1 that the wireless powertransmitter (100) directly transfers (or transmits) power to thewireless power receiver (200), the wireless power system (10) may alsobe equipped with a separate wireless power transceiver, such as a relayor repeater, for increasing a wireless power transport distance betweenthe wireless power transmitter (100) and the wireless power receiver(200). In this case, power is delivered to the wireless powertransceiver from the wireless power transmitter (100), and, then, thewireless power transceiver may transfer the received power to thewireless power receiver (200).

Hereinafter, the terms wireless power receiver, power receiver, andreceiver, which are mentioned in this specification, will refer to thewireless power receiver (200). Also, the terms wireless powertransmitter, power transmitter, and transmitter, which are mentioned inthis specification, will refer to the wireless power transmitter (100).

FIG. 3 shows an exemplary embodiment of diverse electronic devicesadopting a wireless power transmission system.

As shown in FIG. 3 , the electronic devices included in the wirelesspower transmission system are sorted in accordance with the amount oftransmitted power and the amount of received power. Referring to FIG. 3, wearable devices, such as smart watches, smart glasses, head mounteddisplays (HMDs), smart rings, and so on, and mobile electronic devices(or portable electronic devices), such as earphones, remote controllers,smartphones, PDAs, tablet PCs, and so on, may adopt a low-power(approximately 5 W or less or approximately 20 W or less) wirelesscharging method.

Small-sized/Mid-sized electronic devices, such as laptop computers,robot vacuum cleaners, TV receivers, audio devices, vacuum cleaners,monitors, and so on, may adopt a mid-power (approximately 50 W or lessor approximately 200 W or less) wireless charging method. Kitchenappliances, such as mixers, microwave ovens, electric rice cookers, andso on, and personal transportation devices (or other electric devices ormeans of transportation), such as powered wheelchairs, powered kickscooters, powered bicycles, electric cars, and so on may adopt ahigh-power (approximately 2 kW or less or approximately 22 kW or less)wireless charging method.

The electric devices or means of transportation, which are describedabove (or shown in FIG. 1 ) may each include a wireless power receiver,which will hereinafter be described in detail. Therefore, theabove-described electric devices or means of transportation may becharged (or re-charged) by wirelessly receiving power from a wirelesspower transmitter.

Hereinafter, although the this specification will be described based ona mobile device adopting the wireless power charging method, this ismerely exemplary. And, therefore, it shall be understood that thewireless charging method according to this specification may be appliedto diverse electronic devices.

Wireless power transmitters and receivers may provide a very convenientuser experience and interface (UX/UI). That is, a smart wirelesscharging service may be provided, and the smart wireless chargingservice may be implemented based on a UX/UI of a smartphone including awireless power transmitter. For these applications, an interface betweena processor of a smartphone and a wireless charging receiver allows for“drop and play” two-way communication between the wireless powertransmitter and the wireless power receiver.

As an example, a user may experience a smart wireless charging servicein a hotel. When the user enters a hotel room and puts a smartphone on awireless charger in the room, the wireless charger transmits wirelesspower to the smartphone and the smartphone receives wireless power. Inthis process, the wireless charger transmits information on the smartwireless charging service to the smartphone. When it is detected thatthe smartphone is located on the wireless charger, when it is detectedthat wireless power is received, or when the smartphone receivesinformation on the smart wireless charging service from the wirelesscharger, the smartphone enters a state of inquiring the user aboutagreement (opt-in) of supplemental features. To this end, the smartphonemay display a message on a screen in a manner with or without an alarmsound. An example of the message may include the phrase “Welcome to###hotel. Select” Yes” to activate smart charging functions: Yes|NoThanks.” The smartphone receives an input from the user who selects Yesor No Thanks, and performs a next procedure selected by the user. If Yesis selected, the smartphone transmits corresponding information to thewireless charger. The smartphone and the wireless charger perform thesmart charging function together.

The smart wireless charging service may also include receiving WiFicredentials auto-filled. For example, the wireless charger transmits theWiFi credentials to the smartphone, and the smartphone automaticallyinputs the WiFi credentials received from the wireless charger byrunning an appropriate application.

The smart wireless charging service may also include running a hotelapplication that provides hotel promotions or obtaining remotecheck-in/check-out and contact information.

As another example, the user may experience the smart wireless chargingservice in a vehicle. When the user gets in the vehicle and puts thesmartphone on the wireless charger, the wireless charger transmitswireless power to the smartphone and the smartphone receives wirelesspower. In this process, the wireless charger transmits information onthe smart wireless charging service to the smartphone. When it isdetected that the smartphone is located on the wireless charger, whenwireless power is detected to be received, or when the smartphonereceives information on the smart wireless charging service from thewireless charger, the smartphone enters a state of inquiring the userabout checking identity.

In this state, the smartphone is automatically connected to the vehiclevia WiFi and/or Bluetooth. The smartphone may display a message on thescreen in a manner with or without an alarm sound. An example of themessage may include a phrase of “Welcome to your car. Select “Yes” tosynch device with in-car controls: Yes No Thanks.” Upon receiving theuser's input to select Yes or No Thanks, the smartphone performs a nextprocedure selected by the user. If Yes is selected, the smartphonetransmits corresponding information to the wireless charger. Inaddition, the smartphone and the wireless charger may run an in-vehiclesmart control function together by driving in-vehicleapplication/display software. The user may enjoy the desired music andcheck a regular map location. The in-vehicle applications/displaysoftware may include an ability to provide synchronous access forpassers-by.

As another example, the user may experience smart wireless charging athome. When the user enters the room and puts the smartphone on thewireless charger in the room, the wireless charger transmits wirelesspower to the smartphone and the smartphone receives wireless power. Inthis process, the wireless charger transmits information on the smartwireless charging service to the smartphone. When it is detected thatthe smartphone is located on the wireless charger, when wireless poweris detected to be received, or when the smartphone receives informationon the smart wireless charging service from the wireless charger, thesmartphone enters a state of inquiring the user about agreement (opt-in)of supplemental features. To this end, the smartphone may display amessage on the screen in a manner with or without an alarm sound. Anexample of the message may include a phrase such as “Hi xxx, Would youlike to activate night mode and secure the building?: Yes No Thanks.”The smartphone receives a user input to select Yes or No Thanks andperforms a next procedure selected by the user. If Yes is selected, thesmartphone transmits corresponding information to the wireless charger.The smartphones and the wireless charger may recognize at least user'spattern and recommend the user to lock doors and windows, turn offlights, or set an alarm.

A standard for the wireless power transfer (or transmission) includes awireless power consortium (WPC), an air fuel alliance (AFA), and a powermatters alliance (PMA).

The WPC standard defines a baseline power profile (BPP) and an extendedpower profile (EPP). The BPP is related to a wireless power transmitterand a wireless power receiver supporting a power transfer of 5 W, andthe EPP is related to a wireless power transmitter and a wireless powerreceiver supporting the transfer of a power range greater than 5 W andless than 30 W.

Diverse wireless power transmitters and wireless power receivers eachusing a different power level may be covered by each standard and may besorted by different power classes or categories.

For example, the WPC may categorize (or sort) the wireless powertransmitters and the wireless power receivers as PC-1, PC0, PC1, andPC2, and the WPC may provide a standard document (or specification) foreach power class (PC). The PC-1 standard relates to wireless powertransmitters and receivers providing a guaranteed power of less than 5W. The application of PC-1 includes wearable devices, such as smartwatches.

The PC0 standard relates to wireless power transmitters and receiversproviding a guaranteed power of 5 W. The PC0 standard includes an EPPhaving a guaranteed power ranges that extends to 30 W. Although in-band(IB) communication corresponds to a mandatory communication protocol ofPC0, out-of-band (OBB) communication that is used as an optional backupchannel may also be used for PC0. The wireless power receiver may beidentified by setting up an OOB flag, which indicates whether or not theOOB is supported, within a configuration packet. A wireless powertransmitter supporting the OOB may enter an OOB handover phase bytransmitting a bit-pattern for an OOB handover as a response to theconfiguration packet. The response to the configuration packet maycorrespond to an NAK, an ND, or an 8-bit pattern that is newly defined.The application of the PC0 includes smartphones.

The PC1 standard relates to wireless power transmitters and receiversproviding a guaranteed power ranging from 30 W to 150 W. OOB correspondsto a mandatory communication channel for PC1, and IB is used forinitialization and link establishment to OOB. The wireless powertransmitter may enter an OOB handover phase by transmitting abit-pattern for an OOB handover as a response to the configurationpacket. The application of the PC1 includes laptop computers or powertools.

The PC2 standard relates to wireless power transmitters and receiversproviding a guaranteed power ranging from 200 W to 2 kW, and itsapplication includes kitchen appliances.

As described above, the PCs may be differentiated in accordance with therespective power levels. And, information on whether or not thecompatibility between the same PCs is supported may be optional ormandatory. Herein, the compatibility between the same PCs indicates thatpower transmission/reception between the same PCs is possible. Forexample, in case a wireless power transmitter corresponding to PC x iscapable of performing charging of a wireless power receiver having thesame PC x, it may be understood that compatibility is maintained betweenthe same PCs. Similarly, compatibility between different PCs may also besupported. Herein, the compatibility between different PCs indicatesthat power transmission/reception between different PCs is alsopossible. For example, in case a wireless power transmittercorresponding to PC x is capable of performing charging of a wirelesspower receiver having PC y, it may be understood that compatibility ismaintained between the different PCs.

The support of compatibility between PCs corresponds to an extremelyimportant issue in the aspect of user experience and establishment ofinfrastructure. Herein, however, diverse problems, which will bedescribed below, exist in maintaining the compatibility between PCs.

In case of the compatibility between the same PCs, for example, in caseof a wireless power receiver using a lap-top charging method, whereinstable charging is possible only when power is continuously transferred,even if its respective wireless power transmitter has the same PC, itmay be difficult for the corresponding wireless power receiver to stablyreceive power from a wireless power transmitter of the power toolmethod, which transfers power non-continuously. Additionally, in case ofthe compatibility between different PCs, for example, in case a wirelesspower transmitter having a minimum guaranteed power of 200 W transferspower to a wireless power receiver having a maximum guaranteed power of5 W, the corresponding wireless power receiver may be damaged due to anovervoltage. As a result, it may be inappropriate (or difficult) to usethe PS as an index/reference standard representing/indicating thecompatibility.

Hereinafter, ‘profiles’ will be newly defined based on indexes/referencestandards representing/indicating the compatibility. More specifically,it may be understood that by maintaining compatibility between wirelesspower transmitters and receivers having the same ‘profile’, stable powertransmission/reception may be performed, and that powertransmission/reception between wireless power transmitters and receivershaving different ‘profiles’ cannot be performed. The ‘profiles’ may bedefined in accordance with whether or not compatibility is possibleand/or the application regardless of (or independent from) the powerclass.

For example, the profile may be sorted into 4 different categories, suchas i) Mobile, ii) Power tool, iii) Kitchen, and iv) Wearable.

In case of the ‘Mobile’ profile, the PC may be defined as PC0 and/orPC1, the communication protocol/method may be defined as D3 and OOBcommunication, and the operation frequency may be defined as 87 to 205kHz, and smartphones, laptop computers, and so on, may exist as theexemplary application.

In case of the ‘Power tool’ profile, the PC may be defined as PC1, thecommunication protocol/method may be defined as D3 communication, andthe operation frequency may be defined as 87 to 145 kHz, and powertools, and so on, may exist as the exemplary application.

In case of the ‘Kitchen’ profile, the PC may be defined as PC2, thecommunication protocol/method may be defined as NFC-based communication,and the operation frequency may be defined as less than 100 kHz, andkitchen/home appliances, and so on, may exist as the exemplaryapplication.

In case of the ‘Wearable’ profile, the PC may be defined as PC-1, thecommunication protocol/method may be defined as D3 communication, andthe operation frequency may be defined as 87 to 205 kHz, and wearabledevices that are worn by the users, and so on, may exist as theexemplary application.

It may be mandatory to maintain compatibility between the same profiles,and it may be optional to maintain compatibility between differentprofiles.

The above-described profiles (Mobile profile, Power tool profile,Kitchen profile, and Wearable profile) may be generalized and expressedas first to nth profile, and a new profile may be added/replaced inaccordance with the WPC standard and the exemplary embodiment.

In case the profile is defined as described above, the wireless powertransmitter may optionally perform power transmission only to thewireless power receiving corresponding to the same profile as thewireless power transmitter, thereby being capable of performing a morestable power transmission. Additionally, since the load (or burden) ofthe wireless power transmitter may be reduced and power transmission isnot attempted to a wireless power receiver for which compatibility isnot possible, the risk of damage in the wireless power receiver may bereduced.

PC1 of the ‘Mobile’ profile may be defined by being derived from anoptional extension, such as OOB, based on PC0. And, the ‘Power tool’profile may be defined as a simply modified version of the PC1 ‘Mobile’profile. Additionally, up until now, although the profiles have beendefined for the purpose of maintaining compatibility between the sameprofiles, in the future, the technology may be evolved to a level ofmaintaining compatibility between different profiles. The wireless powertransmitter or the wireless power receiver may notify (or announce) itsprofile to its counterpart by using diverse methods.

In the AFA standard, the wireless power transmitter is referred to as apower transmitting unit (PTU), and the wireless power receiver isreferred to as a power receiving unit (PRU). And, the PTU is categorizedto multiple classes, as shown in Table 1, and the PRU is categorized tomultiple classes, as shown in Table 2.

TABLE 1 Minimum value for a maximum Minimum category number ofP_(TX)_IN_MAX support requirement supported devices Class 1  2 W 1×Category 1 1× Category 1 Class 2 10 W 1× Category 3 2× Category 2 Class3 16 W 1× Category 4 2× Category 3 Class 4 33 W 1× Category 5 3×Category 3 Class 5 50 W 1× Category 6 4× Category 3 Class 6 70 W 1×Category 7 5× Category 3

TABLE 2 PRU P_(RX)_OUT_MAX′ Exemplary application Category 1 TBDBluetooth headset Category 2 3.5 W Feature phone Category 3 6.5 WSmartphone Category 4 13 W Tablet PC, Phablet Category 5 25 W Small formfactor laptop Category 6 37.5 W General laptop Category 7 50 W Homeappliance

As shown in Table 1, a maximum output power capability of Class n PTUmay be equal to or greater than the PTX_IN_MAX of the correspondingclass. The PRU cannot draw a power that is higher than the power levelspecified in the corresponding category. FIG. 4 is a block diagram of awireless power transmission system according to another embodiment.

Referring to FIG. 4 , the wireless power transmission system (10)includes a mobile device (450), which wirelessly receives power, and abase station (400), which wirelessly transmits power.

As a device providing induction power or resonance power, the basestation (400) may include at least one of a wireless power transmitter(100) and a system unit (405). The wireless power transmitter (100) maytransmit induction power or resonance power and may control thetransmission. The wireless power transmitter (100) may include a powerconversion unit (110) converting electric energy to a power signal bygenerating a magnetic field through a primary coil (or primary coils),and a communications & control unit (120) controlling the communicationand power transfer between the wireless power receiver (200) in order totransfer power at an appropriate (or suitable) level. The system unit(405) may perform input power provisioning, controlling of multiplewireless power transmitters, and other operation controls of the basestation (400), such as user interface control.

The primary coil may generate an electromagnetic field by using analternating current power (or voltage or current). The primary coil issupplied with an alternating current power (or voltage or current) of aspecific frequency, which is being outputted from the power conversionunit (110). And, accordingly, the primary coil may generate a magneticfield of the specific frequency. The magnetic field may be generated ina non-radial shape or a radial shape. And, the wireless power receiver(200) receives the generated magnetic field and then generates anelectric current. In other words, the primary coil wirelessly transmitspower.

In the magnetic induction method, a primary coil and a secondary coilmay have randomly appropriate shapes. For example, the primary coil andthe secondary coil may correspond to copper wire being wound around ahigh-permeability formation, such as ferrite or a non-crystalline metal.The primary coil may also be referred to as a primary core, a primarywinding, a primary loop antenna, and so on. Meanwhile, the secondarycoil may also be referred to as a secondary core, a secondary winding, asecondary loop antenna, a pickup antenna, and so on.

In case of using the magnetic resonance method, the primary coil and thesecondary coil may each be provided in the form of a primary resonanceantenna and a secondary resonance antenna. The resonance antenna mayhave a resonance structure including a coil and a capacitor. At thispoint, the resonance frequency of the resonance antenna may bedetermined by the inductance of the coil and a capacitance of thecapacitor. Herein, the coil may be formed to have a loop shape. And, acore may be placed inside the loop. The core may include a physicalcore, such as a ferrite core, or an air core.

The energy transmission (or transfer) between the primary resonanceantenna and the second resonance antenna may be performed by a resonancephenomenon occurring in the magnetic field. When a near fieldcorresponding to a resonance frequency occurs in a resonance antenna,and in case another resonance antenna exists near the correspondingresonance antenna, the resonance phenomenon refers to a highly efficientenergy transfer occurring between the two resonance antennas that arecoupled with one another. When a magnetic field corresponding to theresonance frequency is generated between the primary resonance antennaand the secondary resonance antenna, the primary resonance antenna andthe secondary resonance antenna resonate with one another. And,accordingly, in a general case, the magnetic field is focused toward thesecond resonance antenna at a higher efficiency as compared to a casewhere the magnetic field that is generated from the primary antenna isradiated to a free space. And, therefore, energy may be transferred tothe second resonance antenna from the first resonance antenna at a highefficiency. The magnetic induction method may be implemented similarlyto the magnetic resonance method. However, in this case, the frequencyof the magnetic field is not required to be a resonance frequency.Nevertheless, in the magnetic induction method, the loops configuringthe primary coil and the secondary coil are required to match oneanother, and the distance between the loops should be very close-ranged.

Although it is not shown in the drawing, the wireless power transmitter(100) may further include a communication antenna. The communicationantenna may transmit and/or receive a communication signal by using acommunication carrier apart from the magnetic field communication. Forexample, the communication antenna may transmit and/or receivecommunication signals corresponding to Wi-Fi, Bluetooth, Bluetooth LE,ZigBee, NFC, and so on.

The communications & control unit (120) may transmit and/or receiveinformation to and from the wireless power receiver (200). Thecommunications & control unit (120) may include at least one of an D3communication module and an OOB communication module.

The D3 communication module may transmit and/or receive information byusing a magnetic wave, which uses a specific frequency as its centerfrequency. For example, the communications & control unit (120) mayperform in-band (IB) communication by loading information in themagnetic wave and by transmitting the information through the primarycoil or by receiving a magnetic wave carrying information through theprimary coil. At this point, the communications & control unit (120) mayload information in the magnetic wave or may interpret the informationthat is carried by the magnetic wave by using a modulation scheme, suchas binary phase shift keying (BPSK) or amplitude shift keying (ASK), andso on, or a coding scheme, such as Manchester coding ornon-return-to-zero level (NZR-L) coding, and so on. By using theabove-described D3 communication, the communications & control unit(120) may transmit and/or receive information to distances of up toseveral meters at a data transmission rate of several kbps.

The OOB communication module may also perform out-of-band communicationthrough a communication antenna. For example, the communications &control unit (120) may be provided to a near field communication module.Examples of the near field communication module may includecommunication modules, such as Wi-Fi, Bluetooth, Bluetooth LE, ZigBee,NFC, and so on.

The communications & control unit (120) may control the overalloperations of the wireless power transmitter (100). The communications &control unit (120) may perform calculation and processing of diverseinformation and may also control each configuration element of thewireless power transmitter (100).

The communications & control unit (120) may be implemented in a computeror a similar device as hardware, software, or a combination of the same.When implemented in the form of hardware, the communications & controlunit (120) may be provided as an electronic circuit performing controlfunctions by processing electrical signals. And, when implemented in theform of software, the communications & control unit (120) may beprovided as a program that operates the communications & control unit(120).

By controlling the operation point, the communications & control unit(120) may control the transmitted power. The operation point that isbeing controlled may correspond to a combination of a frequency (orphase), a duty cycle, a duty ratio, and a voltage amplitude. Thecommunications & control unit (120) may control the transmitted power byadjusting any one of the frequency (or phase), the duty cycle, the dutyratio, and the voltage amplitude. Additionally, the wireless powertransmitter (100) may supply a consistent level of power, and thewireless power receiver (200) may control the level of received power bycontrolling the resonance frequency.

The mobile device (450) includes a wireless power receiver (200)receiving wireless power through a secondary coil, and a load (455)receiving and storing the power that is received by the wireless powerreceiver (200) and supplying the received power to the device.

The wireless power receiver (200) may include a power pick-up unit (210)and a communications & control unit (220). The power pick-up unit (210)may receive wireless power through the secondary coil and may convertthe received wireless power to electric energy. The power pick-up unit(210) rectifies the alternating current (AC) signal, which is receivedthrough the secondary coil, and converts the rectified signal to adirect current (DC) signal. The communications & control unit (220) maycontrol the transmission and reception of the wireless power (transferand reception of power).

The secondary coil may receive wireless power that is being transmittedfrom the wireless power transmitter (100). The secondary coil mayreceive power by using the magnetic field that is generated in theprimary coil. Herein, in case the specific frequency corresponds aresonance frequency, magnetic resonance may occur between the primarycoil and the secondary coil, thereby allowing power to be transferredwith greater efficiency.

Although it is not shown in FIG. 4 , the communications & control unit(220) may further include a communication antenna. The communicationantenna may transmit and/or receive a communication signal by using acommunication carrier apart from the magnetic field communication. Forexample, the communication antenna may transmit and/or receivecommunication signals corresponding to Wi-Fi, Bluetooth, Bluetooth LE,ZigBee, NFC, and so on.

The communications & control unit (220) may transmit and/or receiveinformation to and from the wireless power transmitter (100). Thecommunications & control unit (220) may include at least one of an D3communication module and an OOB communication module.

The D3 communication module may transmit and/or receive information byusing a magnetic wave, which uses a specific frequency as its centerfrequency. For example, the communications & control unit (220) mayperform D3 communication by loading information in the magnetic wave andby transmitting the information through the secondary coil or byreceiving a magnetic wave carrying information through the secondarycoil. At this point, the communications & control unit (120) may loadinformation in the magnetic wave or may interpret the information thatis carried by the magnetic wave by using a modulation scheme, such asbinary phase shift keying (BPSK) or amplitude shift keying (ASK), and soon, or a coding scheme, such as Manchester coding or non-return-to-zerolevel (NZR-L) coding, and so on. By using the above-described D3communication, the communications & control unit (220) may transmitand/or receive information to distances of up to several meters at adata transmission rate of several kbps.

The OOB communication module may also perform out-of-band communicationthrough a communication antenna. For example, the communications &control unit (220) may be provided to a near field communication module.

Examples of the near field communication module may includecommunication modules, such as Wi-Fi, Bluetooth, Bluetooth LE, ZigBee,NFC, and so on.

The communications & control unit (220) may control the overalloperations of the wireless power receiver (200). The communications &control unit (220) may perform calculation and processing of diverseinformation and may also control each configuration element of thewireless power receiver (200).

The communications & control unit (220) may be implemented in a computeror a similar device as hardware, software, or a combination of the same.When implemented in the form of hardware, the communications & controlunit (220) may be provided as an electronic circuit performing controlfunctions by processing electrical signals. And, when implemented in theform of software, the communications & control unit (220) may beprovided as a program that operates the communications & control unit(220).

The load (455) may correspond to a battery. The battery may store energyby using the power that is being outputted from the power pick-up unit(210). Meanwhile, the battery is not mandatorily required to be includedin the mobile device (450). For example, the battery may be provided asa detachable external feature. As another example, the wireless powerreceiver may include an operating means that can execute diversefunctions of the electronic device instead of the battery.

As shown in the drawing, although the mobile device (450) is illustratedto be included in the wireless power receiver (200) and the base station(400) is illustrated to be included in the wireless power transmitter(100), in a broader meaning, the wireless power receiver (200) may beidentified (or regarded) as the mobile device (450), and the wirelesspower transmitter (100) may be identified (or regarded) as the basestation (400).

Hereinafter, the coil or coil unit includes a coil and at least onedevice being approximate to the coil, and the coil or coil unit may alsobe referred to as a coil assembly, a coil cell, or a cell.

FIG. 5 is a state transition diagram for describing a wireless powertransfer procedure.

Referring to FIG. 5 , the power transmission (or transfer) from thewireless power transmitter to the wireless power receiver according toan embodiment may be broadly divided into a selection phase (510), aping phase (520), an identification and configuration phase (530), anegotiation phase (540), a calibration phase (550), a power transferphase (560), and a renegotiation phase (570).

If a specific error or a specific event is detected when the powertransfer is initiated or while maintaining the power transfer, theselection phase (510) may include a shifting phase (or step)-referencenumerals S502, S504, S508, S510, and S512. Herein, the specific error orspecific event will be specified in the following description.Additionally, during the selection phase (510), the wireless powertransmitter may monitor whether or not an object exists on an interfacesurface. If the wireless power transmitter detects that an object isplaced on the interface surface, the process step may be shifted to theping phase (520). During the selection phase (510), the wireless powertransmitter may transmit an analog ping having an extremely short pulseand may detect whether or not an object exists within an active area ofthe interface surface based on a current change in the transmitting coilor the primary coil.

In case an object is sensed (or detected) in the selection phase (510),the wireless power transmitter may measure a quality factor of awireless power resonance circuit (e.g., power transmission coil and/orresonance capacitor). According to the embodiment, during the selectionphase (510), the wireless power transmitter may measure the qualityfactor in order to determine whether or not a foreign object exists inthe charging area along with the wireless power receiver. In the coilthat is provided in the wireless power transmitter, inductance and/orcomponents of the series resistance may be reduced due to a change inthe environment, and, due to such decrease, a value of the qualityfactor may also be decreased. In order to determine the presence orabsence of a foreign object by using the measured quality factor value,the wireless power transmitter may receive from the wireless powerreceiver a reference quality factor value, which is measured in advancein a state where no foreign object is placed within the charging area.The wireless power transmitter may determine the presence or absence ofa foreign object by comparing the measured quality factor value with thereference quality factor value, which is received during the negotiationphase (540). However, in case of a wireless power receiver having a lowreference quality factor value—e.g., depending upon its type, purpose,characteristics, and so on, the wireless power receiver may have a lowreference quality factor value-in case a foreign object exists, sincethe difference between the reference quality factor value and themeasured quality factor value is small (or insignificant), a problem mayoccur in that the presence of the foreign object cannot be easilydetermined. Accordingly, in this case, other determination factorsshould be further considered, or the present or absence of a foreignobject should be determined by using another method.

According to another embodiment, in case an object is sensed (ordetected) in the selection phase (510), in order to determine whether ornot a foreign object exists in the charging area along with the wirelesspower receiver, the wireless power transmitter may measure the qualityfactor value within a specific frequency area (e.g., operation frequencyarea). In the coil that is provided in the wireless power transmitter,inductance and/or components of the series resistance may be reduced dueto a change in the environment, and, due to such decrease, the resonancefrequency of the coil of the wireless power transmitter may be changed(or shifted). More specifically, a quality factor peak frequency thatcorresponds to a frequency in which a maximum quality factor value ismeasured within the operation frequency band may be moved (or shifted).

In the ping phase (520), if the wireless power transmitter detects thepresence of an object, the transmitter activates (or Wakes up) areceiver and transmits a digital ping for identifying whether or not thedetected object corresponds to the wireless power receiver. During theping phase (520), if the wireless power transmitter fails to receive aresponse signal for the digital ping—e.g., a signal intensitypacket-from the receiver, the process may be shifted back to theselection phase (510). Additionally, in the ping phase (520), if thewireless power transmitter receives a signal indicating the completionof the power transfer—e.g., charging complete packet-from the receiver,the process may be shifted back to the selection phase (510).

If the ping phase (520) is completed, the wireless power transmitter mayshift to the identification and configuration phase (530) foridentifying the receiver and for collecting configuration and statusinformation.

In the identification and configuration phase (530), if the wirelesspower transmitter receives an unwanted packet (i.e., unexpected packet),or if the wireless power transmitter fails to receive a packet during apredetermined period of time (i.e., out of time), or if a packettransmission error occurs (i.e., transmission error), or if a powertransfer contract is not configured (i.e., no power transfer contract),the wireless power transmitter may shift to the selection phase (510).

The wireless power transmitter may confirm (or verify) whether or notits entry to the negotiation phase (540) is needed based on aNegotiation field value of the configuration packet, which is receivedduring the identification and configuration phase (530). Based on theverified result, in case a negotiation is needed, the wireless powertransmitter enters the negotiation phase (540) and may then perform apredetermined FOD detection procedure. Conversely, in case a negotiationis not needed, the wireless power transmitter may immediately enter thepower transfer phase (560).

In the negotiation phase (540), the wireless power transmitter mayreceive a Foreign Object Detection (FOD) status packet that includes areference quality factor value. Or, the wireless power transmitter mayreceive an FOD status packet that includes a reference peak frequencyvalue. Alternatively, the wireless power transmitter may receive astatus packet that includes a reference quality factor value and areference peak frequency value. At this point, the wireless powertransmitter may determine a quality coefficient threshold value for FOdetection based on the reference quality factor value. The wirelesspower transmitter may determine a peak frequency threshold value for FOdetection based on the reference peak frequency value.

The wireless power transmitter may detect the presence or absence of anFO in the charging area by using the determined quality coefficientthreshold value for FO detection and the currently measured qualityfactor value (i.e., the quality factor value that was measured beforethe ping phase), and, then, the wireless power transmitter may controlthe transmitted power in accordance with the FO detection result. Forexample, in case the FO is detected, the power transfer may be stopped.However, this specification will not be limited only to this.

The wireless power transmitter may detect the presence or absence of anFO in the charging area by using the determined peak frequency thresholdvalue for FO detection and the currently measured peak frequency value(i.e., the peak frequency value that was measured before the pingphase), and, then, the wireless power transmitter may control thetransmitted power in accordance with the FO detection result. Forexample, in case the FO is detected, the power transfer may be stopped.However, this specification will not be limited only to this.

In case the FO is detected, the wireless power transmitter may return tothe selection phase (510). Conversely, in case the FO is not detected,the wireless power transmitter may proceed to the calibration phase(550) and may, then, enter the power transfer phase (560).

More specifically, in case the FO is not detected, the wireless powertransmitter may determine the intensity of the received power that isreceived by the receiving end during the calibration phase (550) and maymeasure power loss in the receiving end and the transmitting end inorder to determine the intensity of the power that is transmitted fromthe transmitting end. In other words, during the calibration phase(550), the wireless power transmitter may estimate the power loss basedon a difference between the transmitted power of the transmitting endand the received power of the receiving end. The wireless powertransmitter according to the embodiment may calibrate the thresholdvalue for the FOD detection by applying the estimated power loss.

In the power transfer phase (560), in case the wireless powertransmitter receives an unwanted packet (i.e., unexpected packet), or incase the wireless power transmitter fails to receive a packet during apredetermined period of time (i.e., time-out), or in case a violation ofa predetermined power transfer contract occurs (i.e., power transfercontract violation), or in case charging is completed, the wirelesspower transmitter may shift to the selection phase (510).

Additionally, in the power transfer phase (560), in case the wirelesspower transmitter is required to reconfigure the power transfer contractin accordance with a status change in the wireless power transmitter,the wireless power transmitter may shift to the renegotiation phase(570). At this point, if the renegotiation is successfully completed,the wireless power transmitter may return to the power transfer phase(560).

The above-described power transfer contract may be configured based onthe status and characteristic information of the wireless powertransmitter and receiver. For example, the wireless power transmitterstatus information may include information on a maximum amount oftransmittable power, information on a maximum number of receivers thatcan be accommodated, and so on. And, the receiver status information mayinclude information on the required power, and so on.

FIG. 6 shows a power control method according to an embodiment.

As shown in FIG. 6 , in the power transfer phase (560), by alternatingthe power transmission and/or reception and communication, the wirelesspower transmitter (100) and the wireless power receiver (200) maycontrol the amount (or size) of the power that is being transferred. Thewireless power transmitter and the wireless power receiver operate at aspecific control point. The control point indicates a combination of thevoltage and the electric current that are provided from the output ofthe wireless power receiver, when the power transfer is performed.

More specifically, the wireless power receiver selects a desired controlpoint, a desired output current/voltage, a temperature at a specificlocation of the mobile device, and so on, and additionally determines anactual control point at which the receiver is currently operating. Thewireless power receiver calculates a control error value by using thedesired control point and the actual control point, and, then, thewireless power receiver may transmit the calculated control error valueto the wireless power transmitter as a control error packet.

Also, the wireless power transmitter may configure/control a newoperation point-amplitude, frequency, and duty cycle-by using thereceived control error packet, so as to control the power transfer.Therefore, the control error packet may be transmitted/received at aconstant time interval during the power transfer phase, and, accordingto the exemplary embodiment, in case the wireless power receiverattempts to reduce the electric current of the wireless powertransmitter, the wireless power receiver may transmit the control errorpacket by setting the control error value to a negative number. And, incase the wireless power receiver intends to increase the electriccurrent of the wireless power transmitter, the wireless power receivertransmit the control error packet by setting the control error value toa positive number. During the induction mode, by transmitting thecontrol error packet to the wireless power transmitter as describedabove, the wireless power receiver may control the power transfer.

In the resonance mode, which will hereinafter be described in detail,the device may be operated by using a method that is different from theinduction mode. In the resonance mode, one wireless power transmittershould be capable of serving a plurality of wireless power receivers atthe same time. However, in case of controlling the power transfer justas in the induction mode, since the power that is being transferred iscontrolled by a communication that is established with one wirelesspower receiver, it may be difficult to control the power transfer ofadditional wireless power receivers. Therefore, in the resonance modeaccording to this specification, a method of controlling the amount ofpower that is being received by having the wireless power transmittercommonly transfer (or transmit) the basic power and by having thewireless power receiver control its own resonance frequency.Nevertheless, even during the operation of the resonance mode, themethod described above in FIG. 6 will not be completely excluded. And,additional control of the transmitted power may be performed by usingthe method of FIG. 6 .

FIG. 7 is a block diagram of a wireless power transmitter according toanother embodiment. This may belong to a wireless power transmissionsystem that is being operated in the magnetic resonance mode or theshared mode. The shared mode may refer to a mode performing aseveral-for-one (or one-to-many) communication and charging between thewireless power transmitter and the wireless power receiver. The sharedmode may be implemented as a magnetic induction method or a resonancemethod.

Referring to FIG. 7 , the wireless power transmitter (700) may includeat least one of a cover (720) covering a coil assembly, a power adapter(730) supplying power to the power transmitter (740), a powertransmitter (740) transmitting wireless power, and a user interface(750) providing information related to power transfer processing andother related information. Most particularly, the user interface (750)may be optionally included or may be included as another user interface(750) of the wireless power transmitter (700).

The power transmitter (740) may include at least one of a coil assembly(760), an impedance matching circuit (770), an inverter (780), acommunication unit (790), and a control unit (710).

The coil assembly (760) includes at least one primary coil generating amagnetic field. And, the coil assembly (760) may also be referred to asa coil cell.

The impedance matching circuit (770) may provide impedance matchingbetween the inverter and the primary coil(s). The impedance matchingcircuit (770) may generate resonance from a suitable frequency thatboosts the electric current of the primary coil(s). In a multi-coilpower transmitter (740), the impedance matching circuit may additionallyinclude a multiplex that routes signals from the inverter to a subset ofthe primary coils. The impedance matching circuit may also be referredto as a tank circuit.

The impedance matching circuit (770) may include a capacitor, aninductor, and a switching device that switches the connection betweenthe capacitor and the inductor. The impedance matching may be performedby detecting a reflective wave of the wireless power that is beingtransferred (or transmitted) through the coil assembly (760) and byswitching the switching device based on the detected reflective wave,thereby adjusting the connection status of the capacitor or the inductoror adjusting the capacitance of the capacitor or adjusting theinductance of the inductor. In some cases, the impedance matching may becarried out even though the impedance matching circuit (770) is omitted.This specification also includes an exemplary embodiment of the wirelesspower transmitter (700), wherein the impedance matching circuit (770) isomitted.

The inverter (780) may convert a DC input to an AC signal. The inverter(780) may be operated as a half-bridge inverter or a full-bridgeinverter in order to generate a pulse wave and a duty cycle of anadjustable frequency. Additionally, the inverter may include a pluralityof stages in order to adjust input voltage levels.

The communication unit (790) may perform communication with the powerreceiver. The power receiver performs load modulation in order tocommunicate requests and information corresponding to the powertransmitter. Therefore, the power transmitter (740) may use thecommunication unit (790) so as to monitor the amplitude and/or phase ofthe electric current and/or voltage of the primary coil in order todemodulate the data being transmitted from the power receiver.

Additionally, the power transmitter (740) may control the output powerto that the data can be transferred through the communication unit (790)by using a Frequency Shift Keying (FSK) method, and so on.

The control unit (710) may control communication and power transfer (ordelivery) of the power transmitter (740). The control unit (710) maycontrol the power transfer by adjusting the above-described operationpoint. The operation point may be determined by, for example, at leastany one of the operation frequency, the duty cycle, and the inputvoltage.

The communication unit (790) and the control unit (710) may each beprovided as a separate unit/device/chipset or may be collectivelyprovided as one unit/device/chip set.

FIG. 8 shows a wireless power receiver according to another embodiment.This may belong to a wireless power transmission system that is beingoperated in the magnetic resonance mode or the shared mode.

Referring to FIG. 8 , the wireless power receiver (800) may include atleast one of a user interface (820) providing information related topower transfer processing and other related information, a powerreceiver (830) receiving wireless power, a load circuit (840), and abase (850) supporting and covering the coil assembly. Most particularly,the user interface (820) may be optionally included or may be includedas another user interface (820) of the wireless power receiver (800).

The power receiver (830) may include at least one of a power converter(860), an impedance matching circuit (870), a coil assembly (880), acommunication unit (890), and a control unit (810).

The power converter (860) may convert the AC power that is received fromthe secondary coil to a voltage and electric current that are suitablefor the load circuit. According to an exemplary embodiment, the powerconverter (860) may include a rectifier. The rectifier may rectify thereceived wireless power and may convert the power from an alternatingcurrent (AC) to a direct current (DC). The rectifier may convert thealternating current to the direct current by using a diode or atransistor, and, then, the rectifier may smooth the converted current byusing the capacitor and resistance. Herein, a full-wave rectifier, ahalf-wave rectifier, a voltage multiplier, and so on, that areimplemented as a bridge circuit may be used as the rectifier.Additionally, the power converter may adapt a reflected impedance of thepower receiver.

The impedance matching circuit (870) may provide impedance matchingbetween a combination of the power converter (860) and the load circuit(840) and the secondary coil. According to an exemplary embodiment, theimpedance matching circuit may generate a resonance of approximately 100kHz, which can reinforce the power transfer. The impedance matchingcircuit (870) may include a capacitor, an inductor, and a switchingdevice that switches the combination of the capacitor and the inductor.The impedance matching may be performed by controlling the switchingdevice of the circuit that configured the impedance matching circuit(870) based on the voltage value, electric current value, power value,frequency value, and so on, of the wireless power that is beingreceived. In some cases, the impedance matching may be carried out eventhough the impedance matching circuit (870) is omitted. Thisspecification also includes an exemplary embodiment of the wirelesspower receiver (200), wherein the impedance matching circuit (870) isomitted.

The coil assembly (880) includes at least one secondary coil, and,optionally, the coil assembly (880) may further include an elementshielding the metallic part of the receiver from the magnetic field.

The communication unit (890) may perform load modulation in order tocommunicate requests and other information to the power transmitter.

For this, the power receiver (830) may perform switching of theresistance or capacitor so as to change the reflected impedance.

The control unit (810) may control the received power. For this, thecontrol unit (810) may determine/calculate a difference between anactual operation point and a desired operation point of the powerreceiver (830). Thereafter, by performing a request for adjusting thereflected impedance of the power transmitter and/or for adjusting anoperation point of the power transmitter, the difference between theactual operation point and the desired operation point may beadjusted/reduced. In case of minimizing this difference, an optimalpower reception may be performed.

The communication unit (890) and the control unit (810) may each beprovided as a separate device/chipset or may be collectively provided asone device/chipset.

FIG. 9 shows a communication frame structure according to an embodiment.This may correspond to a communication frame structure in a shared mode.

Referring to FIG. 9 , in the shared mode, different forms of frames maybe used along with one another. For example, in the shared mode, aslotted frame having a plurality of slots, as shown in (A), and a freeformat frame that does not have a specified format, as shown in (B), maybe used. More specifically, the slotted frame corresponds to a frame fortransmitting short data packets from the wireless power receiver (200)to the wireless power transmitter (100). And, since the free formatframe is not configured of a plurality of slots, the free format framemay correspond to a frame that is capable of performing transmission oflong data packets.

Meanwhile, the slotted frame and the free format frame may be referredto other diverse terms by anyone skilled in the art. For example, theslotted frame may be alternatively referred to as a channel frame, andthe free format frame may be alternatively referred to as a messageframe.

More specifically, the slotted frame may include a sync patternindicating the starting point (or beginning) of a slot, a measurementslot, nine slots, and additional sync patterns each having the same timeinterval that precedes each of the nine slots.

Herein, the additional sync pattern corresponds to a sync pattern thatis different from the sync pattern that indicates the starting point ofthe above-described frame. More specifically, the additional syncpattern does not indicate the starting point of the frame but mayindicate information related to the neighboring (or adjacent) slots(i.e., two consecutive slots positioned on both sides of the syncpattern).

Among the nine slots, each sync pattern may be positioned between twoconsecutive slots. In this case, the sync pattern may provideinformation related to the two consecutive slots.

Additionally, the nine slots and the sync patterns being provided beforeeach of the nine slots may have the same time interval. For example, thenine slots may have a time interval of 50 ms. And, the nine syncpatterns may have a time length of 50 ms.

Meanwhile, the free format frame, as shown in (B) may not have aspecific format apart from the sync pattern indicating the startingpoint of the frame and the measurement slot. More specifically, the freeformat frame is configured to perform a function that is different fromthat of the slotted frame. For example, the free format frame may beused to perform a function of performing communication of long datapackets (e.g., additional owner information packets) between thewireless power transmitter and the wireless power receiver, or, in caseof a wireless power transmitter being configured of multiple coils, toperform a function of selecting any one of the coils.

Hereinafter, a sync pattern that is included in each frame will bedescribed in more detail with reference to the accompanying drawings.

FIG. 10 is a structure of a sync pattern according to an embodiment.

Referring to FIG. 10 , the sync pattern may be configured of a preamble,a start bit, a response field, a type field, an info field, and a paritybit. In FIG. 10 , the start bit is illustrated as ZERO.

More specifically, the preamble is configured of consecutive bits, andall of the bits may be set to 0. In other words, the preamble maycorrespond to bits for matching a time length of the sync pattern.

The number of bits configuring the preamble may be subordinate to theoperation frequency so that the length of the sync pattern can be mostapproximate to 50 ms but within a range that does not exceed 50 ms. Forexample, in case the operation frequency corresponds to 100 kHz, thesync pattern may be configured of two preamble bits, and, in case theoperation frequency corresponds to 105 kHz, the sync pattern may beconfigured of three preamble bits.

The start bit may correspond to a bit that follows the preamble, and thestart bit may indicate ZERO. The ZERO may correspond to a bit thatindicates a type of the sync pattern. Herein, the type of sync patternsmay include a frame sync including information that is related to aframe, and a slot sync including information of the slot. Morespecifically, the sync pattern may be positioned between consecutiveframes and may correspond to a frame sync that indicate a start of theframe, or the sync pattern may be positioned between consecutive slotsamong a plurality of slots configuring the frame and may correspond to async slot including information related to the consecutive slots.

For example, in case the ZERO is equal to 0, this may indicate that thecorresponding slot is a slot sync that is positioned in-between slots.And, in case the ZERO is equal to 1, this may indicate that thecorresponding sync pattern is a frame sync being located in-betweenframes.

A parity bit corresponds to a last bit of the sync pattern, and theparity bit may indicate information on a number of bits configuring thedata fields (i.e., the response field, the type field, and the infofield) that are included in the sync pattern. For example, in case thenumber of bits configuring the data fields of the sync patterncorresponds to an even number, the parity bit may be set to when, and,otherwise (i.e., in case the number of bits corresponds to an oddnumber), the parity bit may be set to 0.

The response field may include response information of the wirelesspower transmitter for its communication with the wireless power receiverwithin a slot prior to the sync pattern. For example, in case acommunication between the wireless power transmitter and the wirelesspower receiver is not detected, the response field may have a value of‘00’. Additionally, if a communication error is detected in thecommunication between the wireless power transmitter and the wirelesspower receiver, the response field may have a value of ‘01’. Thecommunication error corresponds to a case where two or more wirelesspower receivers attempt to access one slot, thereby causing collision tooccur between the two or more wireless power receivers.

Additionally, the response field may include information indicatingwhether or not the data packet has been accurately received from thewireless power receiver. More specifically, in case the wireless powertransmitter has denied the data packet, the response field may have avalue of “10” (10—not acknowledge (NAK)). And, in case the wirelesspower transmitter has confirmed the data packet, the response field mayhave a value of “11” (11-acknowledge (ACK)).

The type field may indicate the type of the sync pattern. Morespecifically, in case the sync pattern corresponds to a first syncpattern of the frame (i.e., as the first sync pattern, in case the syncpattern is positioned before the measurement slot), the type field mayhave a value of ‘1’, which indicates a frame sync.

Additionally, in a slotted frame, in case the sync pattern does notcorrespond to the first sync pattern of the frame, the type field mayhave a value of ‘0’, which indicates a slot sync.

Moreover, the information field may determine the meaning of its valuein accordance with the sync pattern type, which is indicated in the typefield. For example, in case the type field is equal to 1 (i.e., in casethe sync pattern type indicates a frame sync), the meaning of theinformation field may indicate the frame type. More specifically, theinformation field may indicate whether the current frame corresponds toa slotted frame or a free-format frame. For example, in case theinformation field is given a value of ‘00’, this indicates that thecurrent frame corresponds to a slotted frame. And, in case theinformation field is given a value of ‘01’, this indicates that thecurrent frame corresponds to a free-format frame.

Conversely, in case the type field is equal to 0 (i.e., in case the syncpattern type indicates a slot sync), the information field may indicatea state of a next slot, which is positioned after the sync pattern. Morespecifically, in case the next slot corresponds to a slot that isallocated (or assigned) to a specific wireless power receiver, theinformation field is given a value of ‘00’. In case the next slotcorresponds to a slot that is locked, so as to be temporarily used bythe specific wireless power receiver, the information field is given avalue of ‘01’. Alternatively, in case the next slot corresponds to aslot that can be freely used by a random wireless power receiver, theinformation field is given a value of ‘10’.

FIG. 11 shows operation statuses of a wireless power transmitter and awireless power receiver in a shared mode according to an embodiment.

Referring to FIG. 11 , the wireless power receiver operating in theshared mode may be operated in any one of a selection phase (1100), anintroduction phase (1110), a configuration phase (1120), a negotiationphase (1130), and a power transfer phase (1140).

Firstly, the wireless power transmitter according to the embodiment maytransmit a wireless power signal in order to detect the wireless powerreceiver. More specifically, a process of detecting a wireless powerreceiver by using the wireless power signal may be referred to as anAnalog ping.

Meanwhile, the wireless power receiver that has received the wirelesspower signal may enter the selection phase (1100). As described above,the wireless power receiver that has entered the selection phase (1100)may detect the presence or absence of an FSK signal within the wirelesspower signal.

In other words, the wireless power receiver may perform communication byusing any one of an exclusive mode and a shared mode in accordance withthe presence or absence of the FSK signal.

More specifically, in case the FSK signal is included in the wirelesspower signal, the wireless power receiver may operate in the sharedmode, and, otherwise, the wireless power receiver may operate in theexclusive mode.

In case the wireless power receiver operates in the shared mode, thewireless power receiver may enter the introduction phase (1110). In theintroduction phase (1110), the wireless power receiver may transmit acontrol information (CI) packet to the wireless power transmitter inorder to transmit the control information packet during theconfiguration phase, the negotiation phase, and the power transferphase. The control information packet may have a header and informationrelated to control. For example, in the control information packet, theheader may correspond to 0X53.

In the introduction phase (1110), the wireless power receiver performsan attempt to request a free slot for transmitting the controlinformation (CI) packet during the following configuration phase,negotiation phase, and power transfer phase. At this point, the wirelesspower receiver selects a free slot and transmits an initial CI packet.If the wireless power transmitter transmits an ACK as a response to thecorresponding CI packet, the wireless power transmitter enters theconfiguration phase. If the wireless power transmitter transmits a NACKas a response to the corresponding CI packet, this indicates thatanother wireless power receiver is performing communication through theconfiguration and negotiation phase. In this case, the wireless powerreceiver re-attempts to perform a request for a free slot.

If the wireless power receiver receives an ACK as a response to the CIpacket, the wireless power receiver may determine the position of aprivate slot within the frame by counting the remaining sync slots up tothe initial frame sync. In all of the subsequent slot-based frames, thewireless power receiver transmits the CI packet through thecorresponding slot.

If the wireless power transmitter authorizes the entry of the wirelesspower receiver to the configuration phase, the wireless powertransmitter provides a locked slot series for the exclusive usage of thewireless power receiver. This may ensure the wireless power receiver toproceed to the configuration phase without any collision.

The wireless power receiver transmits sequences of data packets, such astwo identification data packets (IDHI and IDLO), by using the lockedslots. When this phase is completed, the wireless power receiver entersthe negotiation phase. During the negotiation state, the wireless powertransmitter continues to provide the locked slots for the exclusiveusage of the wireless power receiver. This may ensure the wireless powerreceiver to proceed to the negotiation phase without any collision.

The wireless power receiver transmits one or more negotiation datapackets by using the corresponding locked slot, and the transmittednegotiation data packet(s) may be mixed with the private data packets.Eventually, the corresponding sequence is ended (or completed) alongwith a specific request (SRQ) packet. When the corresponding sequence iscompleted, the wireless power receiver enters the power transfer phase,and the wireless power transmitter stops the provision of the lockedslots.

In the power transfer phase, the wireless power receiver performs thetransmission of a CI packet by using the allocated slots and thenreceives the power. The wireless power receiver may include a regulatorcircuit. The regulator circuit may be included in acommunication/control unit. The wireless power receiver mayself-regulate a reflected impedance of the wireless power receiverthrough the regulator circuit. In other words, the wireless powerreceiver may adjust the impedance that is being reflected for an amountof power that is requested by an external load. This may prevent anexcessive reception of power and overheating.

In the shared mode, (depending upon the operation mode) since thewireless power transmitter may not perform the adjustment of power as aresponse to the received CI packet, in this case, control may be neededin order to prevent an overvoltage state.

Hereinafter, a method of detecting foreign objects and a method forperforming power calibration will be described.

When a wireless power transmitter transmits wireless power to a wirelesspower receiver using a magnetic field, if foreign objects exist in thevicinity, some of the magnetic field is absorbed into the foreignobjects. That is, some of the wireless power transmitted by the wirelesspower transmitter is supplied to the foreign objects, and the rest issupplied to the wireless power receiver. From the viewpoint of powertransfer efficiency, transmitted power is lost as much as power orenergy absorbed by the foreign objects. In this way, a causalrelationship can be established between the existence of the foreignobjects and the power loss (Ploss), so the wireless power transmittermay detect the foreign objects based on how much power loss occurs. Themethod for detecting foreign objects may be referred to as a method fordetecting foreign objects based on the power loss.

The power lost by the foreign objects may be defined as a value obtainedby subtracting the power (Preceived) actually received by the wirelesspower receiver from the power (Ptransmitted) transmitted from thewireless power transmitter. From the viewpoint of the wireless powertransmitter, since the power (Ptransmitted) transmitted from thewireless power transmitter is known, it is possible to obtain the lostpower by knowing only the power (Preceived) received by the wirelesspower receiver. To this end, the wireless power receiver may notify thewireless power transmitter of the received power (Preceived) bytransmitting the received power packet (RPP) to the wireless powertransmitter.

Meanwhile, the wireless power transmitter and the wireless powerreceiver include various circuit components provided therein and areconstituted as independent devices from each other, but since thewireless power transfer is performed by magnetically coupling betweenthe wireless power transmitter and the wireless power receiver, thewireless power transmitter and the wireless power receiver constituteone wireless power transfer system. However, an error may occur betweenthe transmitted power and received power due to a change in the magneticcoupling according to the actual use environment (signal size,frequency, and duty cycle applied to the wireless power transfer system,distance/position alignment between Tx and the Rx, and the like) of Txand Rx as well as unique physical characteristics of the wireless powertransfer system. The error may be an obstacle to a sophisticateddetection of foreign objects.

Therefore, there is a need for a method of deriving the calibratedtransmitted power and received power by reflecting the uniquecharacteristics of the wireless power transfer system and the change inthe actual use environment, and performing more sophisticated FOD basedon the derived calibrated transmitted power and received power.

FIG. 12 is a flowchart illustrating a method for performing powercalibration and a method for performing FOD according to an embodiment.The method for performing power calibration according to the presentembodiment may be performed in the calibration phase of FIG. 5 . Themethod for performing FOD according to the present embodiment may beperformed in the power transfer phase of FIG. 5 . The method forperforming FOD in the present embodiment may include calibrating powerparameters (transmitted power and/or received power).

Referring to FIG. 12 , the wireless power transmitter or the wirelesspower receiver performs a step 1200 of determining the transmitted powerand received power under two different load conditions.

Here, the two load conditions include a “light load” condition and a“connected load” condition. For example, the load may be a batteryincluded in or connected to the wireless power receiver. Since the lightload is not connected to the wireless power receiver (i.e., an outputdisconnect switch is open), the transmitted power and/or the receivedpower at the light load condition is close to minimum expected outputpower. On the other hand, since the connected load is a state where theload is connected to the wireless power receiver (i.e., an outputopening/closing switch is closed), the transmitted power and/or thereceived power at the connected load condition is close to at themaximum expected output power.

In step S1200, the wireless power transmitter may include determiningfirst transmitted power under the light load condition and determiningfirst received power from first received power packet (RPP) receivedfrom the wireless power receiver, and determining, by the wireless powertransmitter, second transmitted power and determining second receivedpower from a second received power packet (RPP) received from thewireless power transmitter. That is, the wireless power receiverdetermines the first received power under the light load condition,transmits the first received power packet indicating the first receivedpower to the wireless power transmitter, determines the second receivedpower under the connected load condition, and transmits the secondreceived power packet indicating the second received power to thewireless power transmitter.

FIG. 13 is a diagram illustrating a received power packet according toan embodiment.

Referring to FIG. 13 , the received power packet is composed of 3 bytes(24 bits), and a first byte (B0) includes 5 bits of reserved bits and 3bits of a mode field. Second and third bytes B1 and B2 include a fieldindicating the received power value. The mode field indicates underwhich condition the received power value included in the received powerpacket is determined, and may be defined as shown in Table 3, forexample.

TABLE 3 Mode Description ‘000’ Normal value; response requested ‘001’Light load calibration value; response requested ‘010’ Connected loadcalibration value; response requested ‘011’ Reserved ‘100’ Normal value;no response expected

Referring to Table 3, when determining the received power under thelight load condition, the wireless power receiver transmits a mode fieldindicating light load calibration value ‘001’ and a first received powerpacket including the corresponding received power value to the wirelesspower transmitter. Meanwhile, when determining the received power underthe connected load condition, the wireless power receiver transmits amode field indicating connected load calibration value ‘001’ and asecond received power packet including the corresponding received powervalue to the wireless power transmitter.

The wireless power transmitter may determine from the mode field of thereceived power packet received whether the corresponding received powervalue is the received power value under the light load condition or thereceived power value under the connected load condition.

Referring back to FIG. 12 , the wireless power transmitter determines atleast one calibration constant based on power variables (transmittedpower under the light load condition, received power under the lightload condition, transmitted power under the connected load condition,and received power under the connected load condition) determined underthe two load conditions (S1205).

The wireless power transmitter may calibrate the transmitted powerand/or the received power by applying linear interpolation to the powerparameters (transmitted power and/or received power) determined based onthe two load conditions.

When the transmitted power and received power determined under each loadcondition are x and y, respectively, two coordinates (x and y) areobtained. One is first coordinates (x1 and y1) under the light loadcondition, and the other is second coordinates (x2 and y2) under theconnected load condition. These two coordinates are as illustrated in agraph in FIG. 14 .

FIG. 14 illustrates a calibration curve based on linear interpolationaccording to an embodiment.

Referring to FIG. 14 , when a first coordinate composed of transmittedpower (Ptr (light)) and received power (Prec (light)) under the lightload condition and a second coordinate composed of transmitted power(Ptr (light)) and received power (Ptr (connected)) under the connectedload condition are connected to each other by the linear interpolation,a linear curve whose a gradient is a and a y-axis offset is b isderived. Here, a may be called a first calibration constant, and b maybe called a second calibration constant.

The calibration constants a and b may be derived by the calibrationcurve of FIG. 14 , and the derivation process is expressed by thefollowing Equations.

$\begin{matrix}{a = \frac{P_{received}^{({connected})} - P_{received}^{({light})}}{P_{transmitted}^{({connected})} - P_{transmitted}^{({light})}}} & \lbrack {{Equation}1} \rbrack\end{matrix}$ $\begin{matrix}{b = \frac{{P_{transmitted}^{({connected})}P_{received}^{({light})}} - {P_{received}^{({connected})}P_{transmitted}^{({light})}}}{P_{transmitted}^{({connected})} - P_{transmitted}^{({light})}}} & \lbrack {{Equation}2} \rbrack\end{matrix}$

The present embodiment relates to a calibration using the twocoordinates according to the two load conditions, which may also bereferred to as a two point calibration. Also, the calibration curve maybe called a calibration function based on at least one calibrationconstant. Therefore, the step of determining the calibration constantaccording to step S1205 may be referred to as the step of determiningthe calibration function. In addition, the present embodiment uses thelinear interpolation in obtaining the calibration constant, but theinterpolation method is not limited thereto.

Referring back to FIG. 12 , when the calibration constants aredetermined as above, the wireless power transmitter completes thecalibration phase and enters the power transfer phase. The wirelesspower transmitter determines the transmitted power in the power transferphase and receives the received power packet from the wireless powerreceiver. At this time, the wireless power transmitter determines thecalibrated transmitted power and/or received power by calibrating thepower parameters (transmitted power and/or received power) determined inthe power transfer phase using the calibration function (S1210).

In one aspect, the method for determining the calibrated transmittedpower includes determining a scaled transmitted power (a·Ptransmitted)by multiplying the transmitted power (Ptransmitted) determined in thepower transfer phase by the first calibration constant (a), anddetermining calibrated transmitted power (Pcalibrated) by adding thesecond calibration constant (b) to the scaled transmitted power. Themethod for calculating the calibrated transmitted power can be expressedas the following Equation (3).

P _(calibrated) =aP _(transmitted) +b  [Equation 3]

The wireless power transmitter determines the power loss based on thecalibrated power parameters (transmitted power and/or received power),and performs the FOD based on the determined power loss (S1215). Thewireless power transmitter may perform i) the FOD based on thecalibrated transmitted power and the uncalibrated received power,perform ii) the FOD based on the uncalibrated transmitted power and thecalibrated received power, and perform iii) the FOD based on thecalibrated transmitted power and the calibrated received power. In thecase of example i), the wireless power transmitter may determine thepower loss based on a difference value between the calibratedtransmitted power (Pcalibrated) and the uncalibrated received power(Precevied) as in Equation (4).

P _(loss) =P _(calibrated) −P _(received)[Equation 4]

In the case of examples ii) and iii), the wireless power transmitter mayalso determine the calibrated received power in addition to thecalibrated transmitted power.

If the determined power loss exceeds a threshold, the wireless powertransmitter may determine that foreign objects exist and stop powertransfer. On the other hand, if the determined power loss does notexceed the threshold, the wireless power transmitter may determine thatthe foreign objects do not exist and continue the power transfer.

Steps S1200 to S1205 correspond to the calibration phase, and stepsS1210 to S1215 correspond to the power transfer phase. In the presentembodiment, although the calibration phase and the power transfer phaseare divided into separate phases, the calibration phase may be includedin the power transfer phase, and in this case, the calibration may beperformed in the power transfer phase.

The wireless power transmitter in the embodiment according to FIG. 12corresponds to the wireless power transfer device, the wireless powertransmitter, or the power transmitting unit disclosed in FIGS. 1 to 11 .Accordingly, the operation of the wireless power transmitter in thepresent embodiment is implemented by one or two or more combinations ofeach component of the wireless power transmitter in FIGS. 1 to 11 . Forexample, in the present embodiment, an operation of determining thetransmitted power and/or the received power under the two loadconditions according to step S1200, an operation of determining thecalibration constant (or calibration curve or calibration function)according to step S1205, an operation of determining the calibratedtransmitted power and/or received power according to step S1210, and anoperation of performing the FOD according to step S1215 may be performedby the communication/control unit 120.

In addition, the wireless power receiver in the embodiment according toFIG. 12 corresponds to the wireless power transfer device, the wirelesspower transmitter, or the power transmitting unit disclosed in FIGS. 1to 11 . Accordingly, the operation of the wireless power transmitter inthe present embodiment is implemented by one or two or more combinationsof each component of the wireless power receiver in FIGS. 1 to 11 . Forexample, in the present embodiment, an operation of determining thefirst received power under the light load condition and generating thefirst received power packet indicating the first received power andtransmitting the generated first received power packet to the wirelesspower transmitter, and an operation of determining the second receivedpower under the connected load condition and generating the secondreceived power packet indicating the second received power andtransmitting the generated second received power packet to the wirelesspower transmitter may be performed by the communication/control unit220.

In the case of the two point calibration, the power calibration isperformed once in the calibration phase before the power transfer phase,and as a result, the calibration curve may be defined as illustrated inFIG. 14 . If the calibration curve (or calibration constant) is definedonce in the calibration phase, it is estimated that the calibrationconstant and the calibration curve are no longer changed in the powertransfer phase, and all the combinations of transmitted power andreceived power in the power transfer phase in the future correspond toone coordinate on the calibration curve illustrated in FIG. 14 , and thewireless power transmitter uniformly performs the FOD according to thegraph above.

However, there may be a case where the transmitted power and/or thereceived power does not follow a predetermined calibration curve due tovarious causes during power transfer. For example, when the wirelesspower receiver increases the connected load during the power transfer,or when the magnetic coupling between the wireless power transmitter andthe receiver changes sharply, the existing calibration constants andcalibration curves do no longer match new transmitted power and receivedpower according to the changed environment. That is, poor approximationof the overall relationship between transmitted power and received powermay occur. In this case, when the calibrated transmitted power andreceived power are determined based on the ineffective calibrationconstant and the calibration graph, and the FOD is performed based onthe determined transmitted power and received power, the reliability ofthe FOD very deteriorates. In particular, it becomes very difficult todetect foreign objects inserted during the power transfer. However, tochange the calibration curve (or calibration constant), the wirelesspower transmitter and/or the wireless power receiver that returns to theping phase again, and then enters the calibration phase has a problem inthat the wireless charging is interrupted halfway.

Therefore, there is a need for a method capable of adaptively reactingto the newly changed wireless charging environment to detect a powerloss and maintain reliability of FOD. That is, a method for calibratingpower parameters based on adaptive power loss detection (APLD) isrequired.

The method for performing power calibration according to the presentembodiment may include performing the subsequent calibration to increasethe accuracy of the transmitted power and/or the received power that isthe basis of the FOD determination, in a state where the initialcalibration (or initial calibration curve, initial calibration constant,or initial calibration function) for the power parameters is no longereffective due to the increase in power or the change in coupling.

Here, the subsequent calibration may be triggered when a specific eventoccurs. Hereinafter, a specific event that triggers the subsequentcalibration is simply called a trigger event. The trigger event mayindicate a state or a cause that the initial calibration is no longereffective. The subsequent calibration is additionally performed tocorrect or supplement the previously performed calibration. In thissense, the term subsequent calibration is used to be distinguished fromthe initial calibration, and may be replaced by other terms with thesame meaning and function. The trigger event may include various typesdepending on the cause.

As an example, the trigger event may include an event (that is, event inwhich a target rectified voltage (Vrec) increases or even in which thereceived power value increases than the received power value in theprevious load connected condition) in which the load of the wirelesspower receiver is increased to a certain level or higher during thepower transfer over the previous connected load. The trigger event maybe called “load increase event”. The wireless power transmitter and/orthe wireless power receiver may determine whether the load increaseevent occurs, and when the load increase event is detected, may enterthe subsequent calibration phase.

As another example, the trigger event may include an event (for example,event in which the position of the wireless power receiver is sharplychanged) in which the magnetic coupling between the wireless powertransmitter and the wireless power receiver is changed to a certainlevel or higher. The trigger event may be called “coupling changeevent”. The wireless power transmitter and/or the wireless powerreceiver may determine whether the coupling change event occurs, andwhen the coupling change event is detected, may enter the subsequentcalibration phase.

The subsequent calibration phase may be performed in different waysdepending on the type of trigger event.

Subsequent Calibration with Increasing Load

As an example, when the load increase event occurs, the subsequentcalibration in the form of the extension of the initial calibration maybe performed. FIG. 15 illustrates a flowchart of the method forperforming power calibration according to the present embodiment.

FIG. 15 is a flowchart illustrating a method for performing powercalibration according to the load increase event. The method forperforming power calibration according to the present embodiment may beperformed in the power transfer phase of FIG. 5 . The power calibrationin the present embodiment may include calibrating power parameters(transmitted power and/or received power).

Referring to FIG. 15 , the wireless power transmitter transmits thewireless power to the wireless power receiver in the power transferphase (S1500). In the power transfer phase, the wireless power receivertransmits the first received power packet (RPP) in the form of FIG. 13to the wireless power transmitter (S1505). The first received powerpacket includes a mode field, where the mode field may indicate ‘000’ or‘100’ indicating that the received power value corresponds to a normalvalue (see Table 3).

During the power transfer phase over the previous connected load, whenthe load of the wireless power receiver increases above a certain levelor higher (S1510), the wireless power receiver receives the secondreceived power packet and transmits the received second received powerpacket to the wireless power transmitter (S1515). The increase in theload to a certain level or higher may mean that the target rectifiedvoltage (target Vrec) of the wireless power receiver increases to acertain level or higher. Alternatively, the increase in the load to acertain level or higher may mean that the current received power isincreased compared to the received power determined in the initialcalibration phase. Alternatively, step S1510 may be replaced by the casewhere the wireless power received value does not exist in thecalibration curve (or calibration section) according to the initialcalibration. That is, step S1510 may be a case where the received powervalue is greater than the received power value in the previous connectedload condition. This may mean that the received power value is out ofthe range of the existing calibration curve, and therefore the wirelesspower transmitter may no longer perform effective calibration.Therefore, in the subsequent calibration, the wireless power receiverunder the load connected condition transmits the received power value tothe wireless power transmitter so that the wireless power transmittermay perform the subsequent calibration.

The step S1515 may further include determining that the wireless powerreceiver determines that the initial calibration is no longer effective(or effective calibration may not be performed) and connecting the loadmode to a connected load mode, when the power received value is out ofthe initial calibration section.

At this time, the mode field included in the second received powerpacket may indicate ‘010’ indicating that the corresponding receivedpower value is a received power value under the connected loadcondition. That is, the wireless power receiver sets the mode field to‘010’, generates the second received power packet including the modefield, and transmits the generated second received power packet to thewireless power transmitter.

In step S1515, the wireless power receiver may continuously transmit thesecond received power packet to the wireless power transmitterperiodically or for a predetermined time period until an ACK response isreceived from the wireless power transmitter. For example, thepredetermined time period may be 2 seconds. On the other hand, when thewireless power transmitter receives the second received power packet, aNAK response is transmitted until the control of the system isstabilized, and then when the control of the system is stabilized, theACK response can be transmitted to the wireless power receiver.

According to the present embodiment, it is allowed to indicate the modefield as ‘010’ in the power transfer phase as well as in the initialcalibration phase before the power transfer phase. That is, the wirelesspower transmitter expects that the mode field received in the powertransfer phase generally indicates ‘000’ or ‘100’, but the wirelesspower transmitter detects that the load increase event has occurred whenreceiving the mode field indicating ‘010’ as an exception (S1520), andenters the subsequent calibration phase (S1525). Specifically, theoperation of the wireless power transmitter is classified as followsaccording to at what phase the received power packet including the modefield indicating ‘010’ is received. That is, when the wireless powertransmitter receives a received power packet indicating a new connectedload mode from the wireless power receiver in the power transfer phase,the wireless power transmitter may perform the subsequent calibrationusing the value. In this case, the calibration section (or range) of thecalibration may increase according to the subsequent calibration.

As an example, when receiving the received power packet including themode field indicating ‘010’ in the initial calibration phase, thewireless power transmitter performs the initial calibration based on thereceived power value under the initial connected load.

As another example, when receiving the received power packet includingthe mode field indicating ‘010’ in the power transfer phase, thewireless power transmitter performs the subsequent calibration based onthe received power value under the changed connected load condition thatthe load increase event has occurred.

Even in the mode field indicating the same value, the interpretation andoperation of the wireless power transmitter may be different accordingto whether the mode field is received in the initial calibration phaseor the power transfer phase. Of course, it is also possible to configureto use a new value (for example, any one of 101-111 values) withoutreusing the mode field value ‘010’, which is used in the initialcalibration phase, in the power transfer phase. In this case, whenreceiving the received power packet including the mode field indicatingthe new value in the power transfer phase, the wireless powertransmitter detects the load increase event (S1520) and enters thesubsequent calibration phase (S1525).

In this way, when the mode field of the received power packet is set toa specific value (any one of 010 or 101-111) in the power transferphase, it may be interpreted as indicating the occurrence of the loadincrease event occurs or the entry into the subsequent calibrationphase.

The wireless power transmitter in the embodiment according to FIG. 15corresponds to the wireless power transfer device, the wireless powertransmitter, or the power transmitting unit disclosed in FIGS. 1 to 11 .Accordingly, the operation of the wireless power transmitter in thepresent embodiment is implemented by one or two or more combinations ofeach component of the wireless power transmitter in FIGS. 1 to 11 . Forexample, in the present embodiment, the operation of transmitting thewireless power to the wireless power receiver in the power transferphase according to step S1500 may be performed by the power conversionunit 110. Also, the operation of receiving the first received powerpacket according to step S1505, the operation of receiving the secondreceived power packet according to step S1515, the operation ofdetecting the load increase event according to step S1520, and theoperation of entering the subsequent calibration phase according to stepS1525 may be performed by the communication/control unit 120.

In addition, the wireless power receiver in the embodiment according toFIG. 15 corresponds to the wireless power receiving device, the wirelesspower receiver, or the power receiving unit disclosed in FIGS. 1 to 11 .Accordingly, the operation of the wireless power transmitter in thepresent embodiment is implemented by one or two or more combinations ofeach component of the wireless power receiver in FIGS. 1 to 11 . Forexample, in the present embodiment, the operation of receiving thewireless power from the wireless power transmitter in the power transferphase according to step S1500 may be performed by the power pickup unit210. In addition, the operation of generating and transmitting the firstreceived power packet according to step S1505, the operation ofincreasing and detecting the load according to step S1510, and theoperation of generating and transmitting the second received powerpacket according to step S1515 may be performed by thecommunication/control unit 220.

Meanwhile, the subsequent calibration phase according to step S1525 isdescribed in more detail with reference to FIG. 16 . In addition,although the subsequent calibration phase according to step S1525 wasseparately divided from the power transfer phase, it is needless to saythat the subsequent calibration phase may be defined as the operationincluded in the power transfer phase without separately division.

FIG. 16 is a flowchart illustrating a method for performing subsequentcalibration of a power transmitter in a wireless power transmitteraccording to an embodiment.

Referring to FIG. 16 , the wireless power transmitter determines thepower parameter (transmitted power and/or received power) under theadditional connected load condition (S1600). The additional connectedload condition means a load condition in a state (or state in which arectified voltage is increased) in which the connected load of thewireless power receiver increases in the power transfer phase. Thetransmitted power under the additional connected load conditioncorresponds to the information already known as the power (Ptransmitted)transmitted by the wireless power transmitter in the power transferphase. The received power under the additional connected load conditionmay be determined as the received power value (Preceived) included inthe second received power packet received in step S1515.

The wireless power transmitter determines a subsequent calibrationconstant based on the initial calibration constant (obtained by stepS1205), the transmitted power determined under the additional loadcondition, and the received power (S1605).

Specifically, the wireless power transmitter may determine thesubsequent calibration constant by applying the linear interpolation tothe determined transmitted power and/or received power, and determinethe calibrated transmitted power and/or received power.

When the transmitted power and the received power determined under theadditional load condition are x′ and y′, respectively, coordinates (x′and y′) are obtained. When the calibration function (or calibrationcurve) obtained under the initial load condition extends from thecoordinates (x′ and y′) by the linear interpolation, it is as shown inFIG. 17 .

FIG. 17 is a diagram illustrating the extended calibration curve basedon the linear interpolation according to an embodiment.

Referring to FIG. 17 , when a first coordinate composed of transmittedpower (Ptr (light)) and received power (Prec (light)) under the lightload condition in the calibration phase and a second coordinate composedof transmitted power (Ptr_connected (1)) and received power(Prece_connected (1)) under the connected load condition in thecalibration phase are connected to each other by the linearinterpolation, a linear curve whose a gradient is a and a y-axis offsetis b is derived. Here, a may be called a first calibration constant, andb may be called a second calibration constant. This is the same as thecalibration curve illustrated in FIG. 14 .

Meanwhile, when the second coordinate of the calibration curve in FIG.14 and the third coordinate composed of transmitted power(Ptr_connected(2)) and received power(Prec_connected(2)) under theadditional connected load condition in the power transfer phase areconnected to each other by the linear interpolation, the calibrationcurve of FIG. 14 is extended, and an extended calibration function witha gradient al is obtained.

Even if the transmitted power and/or the received power increases due tothe increase in load, the calibration curve is also adaptively extendedby a section of Ptr_connected(1) to Ptr_connected(2), the range in whichthe transmitted power and/or the received power can be calibratedincreases, and as a result, the sophisticated FOD can be performed.

The present embodiment relates to the calibration using threecoordinates according to three load conditions (power under light loadcondition in the calibration phase, power under the connected loadconditions in the calibration phase, and power under the connected loadcondition in the power transfer phase), which may be called 3 pointcalibration or multi-point calibration. In addition, the presentembodiment uses the linear interpolation in obtaining the calibrationconstant, but the interpolation method is not limited thereto.

In order to derive the extended calibration function, the wireless powertransmitter should store the calibration constants according to theinitial calibration function already derived in the calibration phase inan internal memory. The wireless power transmitter updates thepreviously stored initial calibration function with the extendedcalibration function.

Referring back to FIG. 16 , when the additional calibration constantsare determined as described above, the wireless power transmitterdetermines the transmitted power in the power transfer phase andreceives the received power packet from the wireless power receiver. Atthis time, the wireless power transmitter determines the calibratedtransmit power and/or received power by performing the subsequentcalibration on the transmitted power and/or the received powerdetermined in the power transfer phase using the extended calibrationfunction (S1610).

The method of determining the transmitted power calibrated according tothe extended calibration function may be adaptively determined accordingto which section the transmitted power belongs. For example, when thetransmitted power is a section of Ptr_connected(1) or lower, thewireless power transmitter may determine the calibrated transmittedpower by applying the gradient a, and when the transmitted power is asection of Ptr_connected(1) or higher, the wireless power transmittermay determine the calibrated transmitted power by applying the gradiental.

When the subsequent calibrated transmitted power and/or received poweris determined, the wireless power transmitter determines the power lossbased on the subsequent calibrated transmitted power and/or receivedpower, and performs the FOD based on the determined power loss (S1615).The wireless power transmitter may perform i) the FOD based on thecalibrated transmitted power and the uncalibrated received power,perform ii) the FOD based on the uncalibrated transmitted power and thecalibrated received power, and perform iii) the FOD based on thecalibrated transmitted power and the calibrated received power.

If the determined power loss exceeds a threshold, the wireless powertransmitter may determine that foreign objects exist and stop powertransfer. On the other hand, if the determined power loss does notexceed the threshold, the wireless power transmitter may determine thatthe foreign objects do not exist and continue the power transfer.

The wireless power transmitter in the embodiment according to FIGS. 16and 17 corresponds to the wireless power transfer device, the wirelesspower transmitter, or the power transmitting unit disclosed in FIGS. 1to 11 . Accordingly, the operation of the wireless power transmitter inthe present embodiment is implemented by one or two or more combinationsof each component of the wireless power transmitter in FIGS. 1 to 11 .For example, in the present embodiment, an operation of determining thetransmit power and/or the received power under the additional loadcondition according to step S1600, an operation of determining theadditional calibration constant (or calibration curve or calibrationfunction) according to step S1605, an operation of determining thesubsequent calibrated transmit power and/or the subsequent calibratedreceived power according to step S1610, and an operation of performingthe FOD according to step S1615 may be performed by thecommunication/control unit 120.

In addition, the wireless power receiver in the embodiment according toFIGS. 16 and 17 corresponds to the wireless power receiving device, thewireless power receiver, or the power receiving unit disclosed in FIGS.1 to 11 . Accordingly, the operation of the wireless power transmitterin the present embodiment is implemented by one or two or morecombinations of each component of the wireless power receiver in FIGS. 1to 11 . For example, in the present embodiment, the operation ofgenerating the received power packet to the wireless power transmitteraccording to step S1610 may be performed by the power conversion unit220.

The subsequent calibration according to the load increase event isperformed in the power transfer phase without returning to the pingphase, and is contrasted with the subsequent calibration according tothe coupling change event returning to the ping phase.

The subsequent calibration according to the embodiment of step S1525 andFIG. 16 may be performed whenever the trigger event occurs during thepower transfer phase. For example, each time the received power value inthe power transfer phase becomes larger than the received power value inthe existing connected load mode, the wireless power transmitter and thewireless power receiver perform the subsequent calibration according tostep S1525 and the embodiment of FIG. 16 .

Subsequent Calibration According to Coupling Change

As an example, when the coupling change event occurs, the subsequentcalibration in the form of redoing the initial calibration may beperformed. For example, after the calibration phase, the location of thewireless power receiver may be changed by the user's intention or may bechanged regardless of the user's intention. The change of the positionof the wireless power receiver eventually causes the coupling changebetween the wireless power transmitter and the receiver. When thecoupling is changed, the initial calibration function (or initialcalibration curve) is no longer effective because the initialcalibration function derived from the power at the light load/connectedload depends on the specific coupling condition. In other words, theinitial calibration function derived under the specific couplingcondition is no longer effective when the coupling condition is changed.

Accordingly, when the coupling change event occurs, the subsequentcalibration includes a process of deriving a substantially new initialcalibration function because the existing initial calibration functioncan no longer be used.

Hereinafter, the method of detecting the occurrence of the couplingchange event and the method of performing the power calibrationaccording to the coupling change event will be described in more detail.FIG. 15 illustrates a flowchart of the method for performing powercalibration according to the present embodiment.

FIG. 18 is a flowchart illustrating a method for performing powercalibration based on a coupling change event according to an embodiment.The method for performing power calibration according to the presentembodiment may be performed in the calibration phase of FIG. 5 . Thepower calibration in the present embodiment may include calibratingpower parameters (transmitted power and/or received power).

Referring to FIG. 18 , the wireless power transmitter transmits thewireless power to the wireless power receiver in the power transferphase (S1800). In the power transfer phase, the wireless power receivertransmits the first received power packet (RPP), the control errorpacket (CEP), and the like in the form of FIG. 13 to the wireless powertransmitter (S1805).

The wireless power transmitter monitors information on power transmittedin the power transfer phase and/or information (or packet) received fromthe wireless power receiver, and detects the occurrence of a couplingchange event based on the monitoring result. (S1810).

As an example, when the transmitted power (Ptransmitted) is increasedeven though there is no increase in received power, the wireless powertransmitter may determine that the coupling change event occurs or thatforeign objects are inserted.

As another example, after the control error (CE) converges to almost 0,when the CE is sharply changed despite no intentional load change in thewireless power receiver, the wireless power transmitter may determinethat the coupling change event occurs or the foreign objects areinserted. At this time, the wireless power transmitter can check whetherthe change in CE is due to a change in the intentional load condition ofthe wireless power receiver based on the mode field of the receivedpower packet (RPP). That is, the wireless power transmitter maydetermine whether the coupling change event occurs based on the CEP andthe RPP.

When the coupling change event (or insertion of foreign objects) isdetected in step S1810, the wireless power transmitter performs theentire FOD procedure again (Q factor-based FOD and APLD) to detect theforeign objects or perform the subsequent calibration. Here, thesubsequent calibration includes an operation of renewing the calibrationfunction (or calibration curve or calibration constant) according to theinitial calibration again.

The wireless power transmitter may perform an operation of transmittinga specific bit pattern response to the wireless power receiver inresponse to the received power packet received in step S1805 to informthe wireless power receiver that a coupling change event occurs (S1815).FSK modulation can be used for transmission of the bit pattern response.For example, the bit pattern response is 8 bits and may be calledattention (ATN) or request for communication (RFC). The wireless powertransmitter sets the bit pattern response to a specific bit value andtransmits the specific bit value to the wireless power receiver torequest the wireless power receiver to transmit the re-ping initiationpacket, draw attention of the wireless power receiver, requesttransmission of a specific packet, or provide a response to the packetreceived from the wireless power receiver.

As an example, an ACK response indicating the request approval isrepresented by a bit pattern of ‘11111111’, a NAK response rejecting therequest is represented by a bit pattern of ‘00000000’, and ND indicatingthat the request is unrecognizable or ineffective may be represented bya bit pattern of ‘01010101’. In addition, the ATN may be defined asvarious 8-bit sized bit patterns except for the bit pattern defined forthe above ACK/NAK/ND response. For example, the ATN may be defined as‘00001111’, ‘11110000’, ‘10101010’, ‘10110110’, ‘00110011’ or‘01001001’. However, this is only an example, and it is needless to saythat the ATN may be configured with various bit patterns.

Since the ATN bit pattern response generally informs the wireless powerreceiver that there is a message to be transmitted by the wireless powertransmitter, the wireless power receiver receives the ATN bit patternresponse, and then, for some reason, the wireless power transmittertransmits a DSR (poll) packet to the wireless power transmitter todetermine whether the wireless power pattern transmits the ATN bitpattern response (S1820).

At this time, the wireless power transmitter requests the wireless powerreceiver to transmit a packet for initiating re-ping (hereinafterreferred to as a re-ping initiation packet) in response to the DSR(poll) packet (S1825). Step S1825 corresponds to the operation requestedby the wireless power transmitter to the wireless power receiver so thatthe wireless power receiver initiates the re-ping. Since the initiatorof the re-ping is the wireless power receiver, the wireless powertransmitter cannot enter the re-ping phase arbitrarily without thepermission of the wireless power receiver, and therefore, as in stepS1825, a process of requesting the wireless power receiver that is theinitiator of the re-ping to initiate the re-ping preemptively performed.

The wireless power receiver that is requested to initiate the re-pinggenerates the re-ping initiation packet and transmits the generatedre-ping initiation packet to the wireless power transmitter (S1830).Here, the re-ping initiation packet may be the end power transfer (EPT)packet for initiating the re-ping.

FIG. 19 is a structural diagram illustrating an EPT packet forinitiating re-ping according to an embodiment.

Referring to FIG. 19 , the EPT packet indicates an EPT code of 1 byte (8bits). The EPT code can indicate various contents according to the bitvalue. In particular, when the bit value is ‘0x0C’, the end of powertransfer for initiating the re-ping may be indicated. ‘0x0C’ is only anexample, and the bit value indicating the termination of the powertransmission for initiating the re-ping may include various embodimentssuch as ‘0x0D’.

Referring back to FIG. 18 , the wireless power transmitter receiving theEPT packet for initiating the re-ping performs the re-ping (S1835). There-ping may be performed after a specific predetermined re-ping delay.At this time, the re-ping delay value may be set, for example, by there-ping time (or delay) packet in the negotiation phase. Alternatively,the re-ping may be performed immediately despite the specificpredetermined re-ping delay. On the other hand, during the process ofperforming the re-ping, even if the wireless power is not supplied tothe wireless power receiver, the wireless power receiver may indicatethat it is charging on the user interface. If the wireless powertransmitter fails to receive the re-ping initiation packet within acertain time in step S1830, the wireless power transmitter may reset thewireless power receiver and perform the entire FOD procedure again.

The re-ping may include transmitting, by the wireless power transmitter,in analog ping signal in the selecting step, detecting and identifyingthe wireless power receiver (at this time, a beep signal indicatingdetection/identification may be output), and performing the FOD based ona Q factor.

Then, the wireless power transmitter and the receiver perform thesubsequent calibration (S1840). The subsequent calibration according tostep S1840 may include the initial calibration described in theembodiment of FIG. 12 . That is, the subsequent calibration of thewireless power transmitter according to step S1840 includes thecalibration operation of the wireless power transmitter according to theembodiment of FIG. 12 , and the subsequent calibration of the wirelesspower transmitter according to step S1840 includes the calibrationoperation of the wireless power receiver according to the embodiment ofFIG. 12 . Accordingly, the subsequent calibration according to thecoupling change event is completed, and the transmitted power and/or thecalibrated received power according to the subsequent calibration aredetermined.

The wireless power transmitter determines the power loss based on thetransmitted power and/or received power determined by the subsequentcalibration, and performs the FOD based on the determined power loss(S1845).

The wireless power transmitter in the embodiment according to FIG. 18corresponds to the wireless power transfer device, the wireless powertransmitter, or the power transmitting unit disclosed in FIGS. 1 to 11 .Accordingly, the operation of the wireless power transmitter in thepresent embodiment is implemented by one or two or more combinations ofeach component of the wireless power transmitter in FIGS. 1 to 11 . Forexample, in the present embodiment, the operation of transmitting thewireless power to the wireless power receiver in the power transferphase according to step S1800 may be performed by the power conversionunit 110. In addition, an operation of receiving the RPP, the CEP, andthe like according to step S1805, an operation of detecting the couplingchange event according to step S1810, an operation of requesting theinitiation of the re-ping according to step S1825, an operation ofreceiving the re-ping initiation packet according to step S1830, anoperation of performing the re-ping according to step S1835, anoperation of performing the subsequent calibration according to stepS1840, and an operation of performing the FOD according to step S1845may be performed by the communication/control unit 120.

In addition, the wireless power receiver in the embodiment according toFIG. 18 corresponds to the wireless power receiving device, the wirelesspower receiver, or the power receiving unit disclosed in FIGS. 1 to 11 .Accordingly, the operation of the wireless power transmitter in thepresent embodiment is implemented by one or two or more combinations ofeach component of the wireless power receiver in FIGS. 1 to 11 . Forexample, in the present embodiment, the operation of receiving thewireless power from the wireless power transmitter in the power transferphase according to step S1800 may be performed by the power pickup unit210. In addition, an operation of generating and transmitting thepackets of the RPP, the CEP, and the like according to step S1805, anoperation of detecting the coupling change event according to stepS1810, an operation of receiving the re-ping initiation requestaccording to step S1825, an operation of generating and transmitting there-ping initiation packet according to step S1830, an operation ofperforming the re-ping according to step S1835, and an operation ofperforming the subsequent calibration according to step S1840 may beperformed by the communication/control unit 220.

The method for performing power calibration according to FIG. 18 is anexample when the wireless power receiver is the initiator of there-ping. However, for the immediate re-ping, the wireless powertransmitter may be the initiator of the re-ping. Accordingly,hereinafter, the method for performing power calibration in the casewhere the initiator of the re-ping is the wireless power transmitter isdisclosed.

FIG. 20 is a flowchart illustrating a method for performing powercalibration based on a coupling change event according to anotherembodiment. The method for performing power calibration according to thepresent embodiment may be performed in the calibration phase of FIG. 5 .The power calibration in the present embodiment may include thecalibration of the transmitted power and the calibration of the receivedpower.

Referring to FIG. 20 , steps S2000 to S2010 are the same as steps S1800to S1810, respectively. However, in the embodiment of FIG. 20 , sincethe wireless power transmitter is the initiator of the re-ping, thewireless power transmitter notifies the re-ping initiation in a bitpattern instead of transmitting the re-ping initiation request to thewireless power receiver as in step S1815 (S2015). In addition, thewireless power transmitter may transmit the re-ping initiation packet tothe wireless power receiver (S2020), and may enter the re-ping stepunilaterally (S2025). At this time, the re-ping initiation packet instep S2020 may have a packet structure including, as, for example, 1byte (8 bits), a first field of 2 bits indicating whether to perform there-ping and a second field of 2 bits indicating the re-ping delay time.Of course, the number of bits included in the first field and the secondfield may be variously modified.

Thereafter, steps S2025 to S2035 are the same as steps S1825 to S1835,respectively.

The wireless power transmitter in the embodiment according to FIG. 20corresponds to the wireless power transfer device, the wireless powertransmitter, or the power transmitting unit disclosed in FIGS. 1 to 11 .Accordingly, the operation of the wireless power transmitter in thepresent embodiment is implemented by one or two or more combinations ofeach component of the wireless power transmitter in FIGS. 1 to 11 . Forexample, in the present embodiment, the operation of transmitting thewireless power to the wireless power receiver in the power transferphase according to step S2000 may be performed by the power conversionunit 110. In addition, an operation of receiving the RPP, the CEP, andthe like according to step S2005, an operation of detecting the couplingchange event according to step S2010, an operation of generating andtransmitting the re-ping initiation instruction according to step S2015,an operation of transmitting the re-ping initiation packet according tostep S2020, an operation of performing the re-ping according to stepS2025, an operation of performing the subsequent calibration accordingto step S2030, and an operation of performing the FOD according to stepS2035 may be performed by the communication/control unit 120.

In addition, the wireless power receiver in the embodiment according toFIG. 20 corresponds to the wireless power receiving device, the wirelesspower receiver, or the power receiving unit disclosed in FIGS. 1 to 11 .Accordingly, the operation of the wireless power transmitter in thepresent embodiment is implemented by one or two or more combinations ofeach component of the wireless power receiver in FIGS. 1 to 11 . Forexample, in the present embodiment, the operation of receiving thewireless power from the wireless power transmitter in the power transferphase according to step S2000 may be performed by the power pickup unit210. In addition, an operation of generating and transmitting thepackets of the RPP, the CEP, and the like according to step S2005, anoperation of detecting the coupling change event according to stepS2010, an operation of receiving the re-ping initiation instructionaccording to step S2015, an operation of receiving the re-pinginitiation packet according to step S2020, an operation of performingthe re-ping according to step S2025, and an operation of performing thesubsequent calibration according to step S2030 may be performed by thecommunication/control unit 220.

The subsequent calibration according to the embodiment of step S1840 orstep S2030 and FIG. 16 may be performed whenever the trigger eventoccurs during the power transfer phase. For example, each time thecoupling change event occurs, the wireless power transmitter and thewireless power receiver may perform the subsequent calibration accordingto the embodiment of step S1840 or step S2030.

In a wireless power transmitting method and device or receiving deviceand method according to embodiments of this specification, because allcomponents or steps are not essential, the wireless power transmittingdevice and method or receiving device and method may be performed byincluding some or all of the above-described components or steps.Further, embodiments of the wireless power transmitting device andmethod or receiving device and method may be performed in combination.Further, it is not necessary that the above components or steps shouldbe performed in the described order, and a step described later may beperformed prior to a step described earlier.

The foregoing description is merely illustrative of the technical ideaof this specification, and various changes and modifications may be madeby those skilled in the art without departing from the essentialcharacteristics of this specification. Therefore, the foregoingembodiments of this specification can be implemented separately or incombination.

Therefore, the embodiments disclosed in this specification are intendedto illustrate rather than to limit the scope of this specification, andthe scope of the technical idea of this specification is not limited bythese embodiments. The scope of protection of this specification shouldbe construed according to the following claims, and all technical ideaswithin the scope of equivalents to claims should be construed as fallingwithin the scope of this specification.

What is claimed is:
 1. A wireless power transmitter, comprising: a powerconversion unit configured to transmit wireless power generated based onmagnetic coupling to a wireless power receiver in a power transferphase; and a communication/control unit configured to: initiate adigital ping to solicit a response from the wireless power receiver,receive, from the wireless power receiver, a first received power packetinforming a first received power value for power calibration, receive,from the wireless power receiver, a second received power packetinforming a second received power value for power calibration, receive,from the wireless power receiver, a subsequent second received powerpacket informing a third received power value for power calibration,perform calibration for a power parameter using at least one of thefirst received power packet, the second received power packet, or thesubsequent second received power packet, and perform a detection of aforeign object using a power loss determined using the power parametersubjected to the calibration.
 2. The wireless power transmitter of claim1, wherein the communication/control unit receives the subsequent secondreceived power packet from the wireless power receiver during the powertransfer phase.
 3. The wireless power transmitter of claim 1, whereinthe second received power value and the third received power value areclose to maximum power.
 4. The wireless power transmitter of claim 1,wherein the communication/control unit transmits a bit patternrequesting an initiation of re-ping to the wireless power receiver basedon the change in the magnetic coupling.
 5. The wireless powertransmitter of claim 4, wherein the communication/control unit receivesa re-ping initiation packet from the wireless power receiver in responseto the bit pattern.
 6. The wireless power transmitter of claim 5,wherein the re-ping initiation packet includes an end power transfer(EPT) packet for initiating the re-ping.
 7. The wireless powertransmitter of claim 1, wherein the second received power packet and thesubsequent second received power packet have a same mode field value. 8.A power calibration method by a wireless power transmitter, comprising:initiating a digital ping to solicit a response from a wireless powerreceiver, receiving, from the wireless power receiver receiving wirelesspower from the wireless power transmitter, a first received power packetinforming a first received power value for power calibration, receiving,from the wireless power receiver, a second received power packetinforming a second received power value for power calibration,receiving, from the wireless power receiver, a subsequent secondreceived power packet informing a third received power value for powercalibration, performing calibration for a power parameter using at leastone of the first received power packet, the second received powerpacket, or the subsequent second received power packet.
 9. The powercalibration method of claim 8, wherein the second received power valueand the third received power value are close to maximum power.
 10. Thepower calibration method of claim 8, wherein the second received powerpacket and the subsequent second received power packet have a same modefield value.
 11. A method for detecting a foreign object by a wirelesspower transmitter, comprising: initiating a digital ping to solicit aresponse from a wireless power receiver, receiving, from the wirelesspower receiver receiving wireless power from the wireless powertransmitter, a first received power packet informing a first receivedpower value for power calibration, receiving, from the wireless powerreceiver, a second received power packet informing a second receivedpower value for power calibration, receiving, from the wireless powerreceiver, a subsequent second received power packet informing a thirdreceived power value for power calibration, performing calibration for apower parameter using at least one of the first received power packet,the second received power packet, or the subsequent second receivedpower packet, and performing the detection of the foreign object using apower loss determined using the power parameter subjected to thecalibration.
 12. The method of claim 11, wherein the second receivedpower value and the third received power value are close to maximumpower.
 13. The method of claim 11, wherein the second received powerpacket and the subsequent second received power packet have a same modefield value.